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RANK (Receptor Activator of Nuclear Factor kB) is expressed on the surface of osteoclasts. Two ligands, macrophage colony-stimulating factor (M-CSF) and RANK ligand (RANK-L), are necessary for the development and maintenance of osteoclasts. M-CSF is a secreted ligand, but RANK-L remains mostly on the surface of the osteoblast/bone marrow stromal cells. It is imperative that the developing osteoclast is in close association to a stromal cell or osteoblast so that RANK expressed on the osteoclast can bind to the RANK-L on the stromal cell or osteoblast. The levels of both RANK-L and RANK can be up-regulated by resorptive signals such as PTH, PGE₂, and 1,25(OH)₂ D₃.

Osteoprotegerin (OPG) is a secreted protein found in many tissues, including bone. It acts as a decoy, competing with RANK for RANK-L. Osteoclastogenesis depends on the balance between RANK-L and OPG. Prostaglandins and parathyroid hormone, which increase RANK-L while decreasing OPG, promote bone resorption. Similarly, TGF-beta, which diminishes RANK-L and enhances OPG expression, decreases osteoclast activity. Estrogen, by dampening M-CSF and stimulating OPG, blunts two distinct pathways necessary for osteoclast formation and survival.

Osteoporosis

Loss of bone in osteoporosis is more rapid in trabecular bone than in cortical bone; vertebrae, because of their prominent trabecular component, are prone to fracture. Note the variation in the width of the vertebrae and the fractures, and that the bone is very porous.

Note the paucity of trabeculae. Most of the section consists of fat. Although the trabeculae are narrow and reduced in number, they consist of normal matrix that is normally mineralized.

How does this lesion differ from osteomalacia? 
In osteomalacia, trabeculae are surrounded by wide osteoid seams because mineralization of osteoid is delayed.

This image illustrates the response of bone to fracture (note new woven bone to the right of the slide). Osteoblasts arise from pluripotent progenitor cells in the periosteum and granulation tissue. They produce woven bone, resulting in a bony callus that stabilizes the fracture site.

Contrast the morphology of the original lamellar bone to that of woven bone. Woven bone contains many more osteocytes, which are haphazardly arranged. The lamellar bone contains empty lacunae. The necrotic lamellar bone and the reactive woven bone are removed by osteoclasts and replaced by new, mature lamellar bone. This process is called remodeling, and occurs over months to years.

What is the significance of the empty lacunae at the ends of the trabecular bone? 
The empty lacunae indicate that the bone is necrotic. (What is the difference between normal lacunae with osteocytes and necrotic empty lacunae? Lacunae actually have osteocytes when normal)

Fractures that occur in bones weakened by disease are called pathologic fractures. The most common cause of pathologic fracture in elderly individuals is osteoporosis. Another differential diagnosis to consider is metastatic cancer. The metastatic cells produce an osteolytic or osteoblastic reaction in the adjacent bone. Many tumors elaborate substances such as RANK-L or IL-6 that directly stimulate osteoclasts resulting in bone weakness and fracture. In this example, metastatic squamous carcinoma cells are seen within the bone.

What is the significance of the osteoclasts in this lesion? 
The presence of osteoclasts and the Howship lacunae in this lesion indicate that there is active resorption of bone. Tumors metastatic to bone commonly result in lytic lesions.

Another cause of pathologic fracture in elderly patients is Paget disease of bone. In this image, the calvaria is markedly thickened by the growth of new bone. In both specimens, the density of the bone is very heterogeneous, varying from rarefied foci to dense regions. This irregular variation in bone density is characteristic of Paget disease of bone. The excess bone produced in this disease is either woven or lamellar bone, which is poorly organized and structurally weak; the skeleton is prone to fracture.

A 40-year-old woman complained of fatigue, weakness and general malaise.   She had pain in wrists, fingers, and knees.   Effected joints were warm on examination (thinking inflammatory), fingers showed fusiform soft tissue swelling, and subcutaneous nodules were present around the elbow.   She felt stiff in the morning.

Synovial fluid was aspirated and had the following characteristics:
Viscosity – low
Color - translucent, yellow
White blood cells - 3000/mm3 with 50% PMN (Polymorphonuclear neutrophils)
No crystals
Bacterial culture - negative

From the synovial fluid results in what category (Group) is this aspirate?

a. normal
b. non-inflammatory
c. inflammatory
d. septic
e. traumatic

As can be seen in the following table, these characteristics, especially the WBC count and differential and being negative for crystals and bacteria, indicate an inflammatory effusion (Group II).

Contrast this image to below, Paget disease of bone. In normal bone, the trabeculae are well organized and consist of lamellar bone. 

Note the marked irregularity of the cement lines in the cortical bone. This mosaic pattern is characteristic of Paget disease of bone. Production and resorption of bone are uncoupled, resulting in the distorted histomorphology seen in this image. Paget disease is a good example of uncoupling of the basic multicellular unit of bone (so is osteoporosis).

Synovial Fluid SoftChalk

The patient was also HLA-DR4 positive, rheumatoid factor (RF) positive at a titer of 1:500 and had an increased erythrocyte sedimentation rate (ESR). (think rheumatoid arthritis)

HLA-DR4 - Specific HLA-DRB1 alleles have been shown to be associated with rheumatoid arthritis.

Rheumatoid factor (RF) is an autoantibody (usually IgM) against the Fc portion of autologous IgG.   About 80% or individuals with rheumatoid arthritis have elevated serum RF.

normal=negative; <1:80 borderline (less specific); If quantified, normal <30 U/L

Erythrocyte sedimentation rate (ESR) is the rate at which RBCs sediment in 1 hour.   The ESR is non-specific, but usually elevated in inflammatory states.    

Other useful tests:

C-Reactive Protein (CRP), another non-specific, but more quantitative measure of inflammation is also in wide-spread use.

Anti-CCP.   Antibodies to citrulline-modified peptides (CCP) have been show to be present in many people with rheumatoid arthritis and rarely in people with other inflammatory diseases or healthy individuals.   The use of this test is increasing.

Which of the following mechanisms plays the most important role in the causation of joint injury in this patient's disease?

a. Activation of neutrophils by phagocytosis of urate crystals.
  b. Inflammation of synovium caused by infection with Borrelia burgdorferi
  c. Inflammation of the synovium caused by TNF
  d. Antibodies against HLA-B27 antigen
  e. Granulomatouse response to long standing Treponema pallidum infection

You are correct, TNF and IL-1 promote accumulation of inflammatory cells in the synovium.  Urate crystals would indicate gouty arthritis, Borrelia burgdorferi is the pathogen in Lyme Disease, HLA-B27 is associated with seronegative ankylosing spondylopathies, and gummatous necrosis suggests tertiary syphilis

4 of the following

• Morning stiffness √
• Arthritis in three or more joint areas √
• Arthritis of hand joints √
• Symmetric arthritis √
• Rheumatoid nodules √
• Serum rheumatoid factor √
• Typical radiographic changes (erosive synovitis)

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Following a wedding a 40-y.o. man woke during the night with severe right foot pain.   At the wedding he danced, ate a lot, and drank wine and liquor.   His right big toe was swollen, red, felt warm, and he could not step on that foot. His father died of heart failure. Patient is obese & has mild hypertension, Type 2 diabetes for 3 years. All these diseases are under control. (sounds like gout/podagra; better get the synovial fluid to check)

• The right first metatarsal joint was swollen, red, warm, and painful to palpation.
• Labs: Serum uric acid was elevated, leukocytosis was present, ESR elevated.
• Arthrocentesis results: Viscosity - low; color - translucent, yellow, WBC 10,000 cells/µL with 50% PMN; no crystals, bacterial culture – negative
• This is a Group II inflammatory arthritis… not gout!

The patient was treated with nonsteroidal antiinflammatory drugs and improved. (Indomethacin or Naproxen)

What is the diagnosis for the foot pain?

a. Bunion
b. Definitely gout
  c. Podogra
  d. Arthritis
  e. Infection

Excellent! You are correct.  Arthritis is the inflammation of any joint.  Acute inflammation is defined with rubor (redness), tumor (swelling), dolor (pain), calor (heat), and functio laesa (loss of function).  This patient exhibits all of the signs for acute inflammation in a joint thus justifying the diagnosis of arthritis.  Podagra is defined as gouty pain in the great toe.  At this point in the clinical presentation, gout may be suspected but cannot be proved without uric acid crystals in the synovial fluid or phagocytized by WBCs so a more general diagnosis of arthritis is better for now.  However, a clinical diagnosis of gout is reasonable with this presentation and finding of elevated serum uric acid.

Examination of the synovial fluid under polarized light may not always reveal uric acid crystals in gout.  The crystals may be sparse, or they may be deposited in soft tissue, and not present in the fluid at time of examination.  Examination of stained sediment in which white blood cells are concentrated, under polarized light can increase the sensitivity of the test.

Bunion
peripheral atherosclerotic disease (arteriosclerosis obliterans)
gout
broken bones
popliteal aneurysm (compressing tibia nerve)
infection
ingrown toe nail
compartment syndrome causing deep fibular nerve entrapment
muscle cramp
compression fracture
tendon tear or rupture in foot
plantar fasciitis

Several of these could involve a joint and, if inflamed, would be considered arthritis.

3 years later the patient with arthritis of the toe comes back.... complaining of blood in the urine and excruciating back pain.

What is the cause of these symptoms?

 a. Diabetic nephropathy
b. Sodium urate stones
c. Uric acid stones
d. Autoimmune kidney disease

Good, you are correct.  The symptoms are caused by uric acid kidney stones.  Urine is normally slightly acidic; possibly slightly more acidic in this diabetic patient increasing the chances of uric acid stone formation.

• Hydrogen atoms at positions 3 and 9 are weakly ionized with pKa values of 10.3 and 5.75
• Solubility effected by pH, temperature and matrix of the fluid

 If you alkalinize the urine, you could get rid of more uric acid (as urate).  So maybe you should decrease the acid content of the urine.

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Monosodium urate (MSU) crystals appear as needle-shaped rods 5-20 µm long (sometimes shorter).   They are strongly birefringent: yellow when oriented parallel to compensator, blue with perpendicular orientation (negative birefringence or elongation).

Uric acid crystals occur at low pH (5-5.5) and are seen in a variety of shapes including rhombic or four-sided flat plates, prisms, oval forms with pointed ends (lemon shaped), wedges, rosettes, and irregular plates.  

• Serum uric acid is the classical test for gout, but it has poor specificity and sensitivity.  
• 90% with hyper-UA do not have gout (PV+ = 10%)
• Serum UA may be normal at the time of an acute attack
• Identification of monosodium urate crystals in the synovial fluid, especially if present within phagocytes, has the highest probability for the diagnosis of gout.
• Gout may mimic septic arthritis & vice versa.  
• Arthrocentesis with adequate fluid for crystal analysis and culture is crucial to the diagnosis.

 A 30 year-old. man was admitted to the hospital with dyspnea, night sweats, fatigue and early satiety.   Physical examination revealed diffuse adenopathy, masses in the abdomen & chest, ascites, & a pleural effusion.     Chest X-rays confirmed adenopathy & sonography confirmed abdominal masses. Burkitt's Lymphoma at an advanced stage was diagnosed from lymph node biopsy & pleural fluid cytology

 Abnormal lab results included   K+ 5.5 mmol/L (3.5-5.0); Uric Acid 14.1 mg/dL (4.4-7.6); LD 2,210 U/L (208-378)

The patient's elevated uric acid concentration is due to:

 a. Interference by LD with the uric acid test
  b. Ingestion of a high protein diet
  c. Kidney failure
  d. Tumor lysis
  e. Inc. catabolism of pyrimidines by the tumor

You are correct, tumor lysis caused the patient's elevated serum uric acid. In humans, uric acid is the major product of the catabolism of purines: adenosine & guanosine.   Sources include dietary and endogenous nucleic acids.   In this patient, the large tumor burden shows substantial lysis as evidenced by the markedly elevated LD.   The purines in the tumor are metabolized to uric acid.

Note that the term tumor lysis syndrome is usually used to describe the massive release of the intracellular contents of tumor cells due to chemotherapy or radiation therapy.  No such treatment is included in the case, but tumor lysis syndrome is still the best answer… not a great question.

• Hyperuricemia is defined as a serum uric acid concentration above the upper limit of normal:
• 6 mg/dL in women & 7 mg/dL in men.
• As levels increase over 8 mg/dL monosodium urate is more likely to precipitate in tissues.
• Gout refers to heterogeneous disorders resulting from tissue deposition of monosodium urate crystals or crystallization of uric acid in the urinary tract.

·       Gout is nine times more common in men than women. Why is this?

   a. Gout shows X-linked inheritance.
  b. The HLA-DR4 is more common in men than in women.
  c. Men are more physically active than women.
  d. Men have higher serum uric acid levels than women and estrogen protects women (until menopause)

·       Very good, you are correct. Men have higher serum uric acid levels than women and estrogen protects women (until menopause)

·       Which of following conditions lead to hyper-uricemia due to an overproduction of uric acid?

·        a. Rhabdomyolysis
  b. Diabetes Mellitus
  c. Salicylate use
  d. Lead intoxication
  e. Alcohol abuse

·       Correct, rhabdomyolysis leads to hyperuricemia. Think Cell turnover

Hyperuricemia may develop because of increased production of uric acid, decreased excretion of uric acid, or both.

• Overproduction - primary hyperuricemia
• Hypoxanthine-guanine phosphoribosyl-transferase deficiency
• Primary idiopathic hyperuricemia (increased production & decreased excretion)
• Overproduction - secondary hyperuricemia
• Proliferative disease; incr. tissue turnover; rhabdomyolysis

• Decreased excretion - secondary hyperuricemia
• Renal insufficiency
• Diabetes mellitus (ketoacidosis)
• Lactic acidosis
• Lead intoxication
• Drugs - salicylates, diuretics, alcohol
• Many more (Lesch Nyhan)
• Hyperuricemia may lead to
• Acute Gouty Arthritis
• Gouty nephropathy

What is the significance of finding inflammatory cells in the joint fluid?

• Quantitation of white blood cells is an important part of synovial fluid analysis, especially because it is the major basis for classification of an effusion as septic, inflammatory, or noninflammatory

Does the history of diabetes and hypertension in this obese patient help in the diagnostic work-up?

• Obesity, diabetes, and hypertension increase the risk factors for many disease.  
• Increased weight can contribute to arthritis
• Acidosis and progressive renal disease in diabetics can contribute to under excretion of uric acid.
• Hyperuricemia is also associated with the use of diuretics, especially thiazides, which are commonly used in the treatment of hypertension.  

Catabolism of Adenine & Guanine

• Uric acid is the end product of purine (adenine and guanine) metabolism
• Humans don't have uricase which converts uric acid to soluble allantoin

Acute Gouty Arthritis

• Gout may mimic septic arthritis & vice versa.  
• Serum uric acid may fluctuate & is often normal at the time of an acute gout attack.  
• The synovial fluid usually has many WBCs & other nonspecific features of joint inflammation.  
• Arthrocentesis with adequate fluid for crystal analysis and culture is crucial to the diagnosis.  
• Monosodium urate crystals (needle-shaped, brightly negatively birefringent crystals, many of them within neutrophils) can be identified in the synovial fluid in most, but not all cases.

Gouty Nephropathy

• About 20% of patients with gout has urinary tract uric acid stones.
• Uric acid formed in acid urine is relatively insoluable; urate at pH >7.0 10x more soluble.  
• Measurement of urine pH and uric acid excretion is important in the investigation of uric acid urolithiasis.  
• Identification of crystals in the urine may be a clue to the nature of the stones in the kidney.
• Pure uric acid stones account for 5-10% of all urinary tract stones and, unlike many of the calcium-containing stones, are radiolucent. 

This is a classic example of primary osteosarcoma. The tumor is from a young patient (growth plate is still evident). Primary osteosarcomas characteristically arise in the metaphysis and destroy the cortex. It is rare for the tumor to extend into the joint.

A 17-year-old white boy presented to his physician with a history of insidious, often transitory pain in the left knee, which had persisted over the last 6 months. He reported that he had been kicked on the knee during a high school soccer match, and he thought that the joint had never recovered from that insult. Over the last several weeks, the pain had become more persistent and intractable, and he thought that there was some swelling just below the knee.

On physical examination, the physician could palpate a hard, bony expansion in the metaphysis of the proximal tibia. The mobility of the knee joint was normal. Radiographs revealed a large area of lucency in the metaphysis of the tibia, which focally destroyed the cortex. A biopsy of the bone lesion and a chest radiograph were ordered.

The core biopsy specimen revealed varied histopathology. In some sections of the mass, malignant cells surrounded by osteoid predominated, as in Image 5, whereas in other sections, malignant cells embedded in cartilaginous matrix predominated, a morphology similar to Image 8. In other sections, large numbers of giant cells were seen, similar to Image 12. This varied histologic profile presented a diagnostic dilemma to the junior pathology resident. She scheduled a consultation with the attending orthopedic pathologist to help formulate a final diagnosis.

The preliminary clinical and radiologic diagnosis, pending a definitive pathologic report, was cancer of the bone. The boy’s mother was not only concerned for her oldest son, but also expressed concern about the possibility that her other children might develop bone cancer. She related that her father had developed primary cancer of the bone in his 8th decade.

Which sex is more commonly affected by primary osteosarcomas, and at which anatomic site do they most commonly arise? 
Osteosarcomas are more common in males, and most commonly arise in the distal femur or proximal tibia (i.e., around the knee).

What is the significance of trauma in this case? 

Osteosarcoma generally manifests with severe, local pain, although in some cases protracted, slowly developing, slight-to-moderate pain and tenderness may be observed. The tumors occur in young, active patients who may have concurrent trauma to bones and joints, and the patient may not seek prompt medical attention.

This osteosarcoma is very dense radiographically, a finding that indicates the tumor is making bone. The tumor results in destruction of the adjacent cortex and extends into the adjacent soft tissue.

Which organ is the preferential site for metastases in patients with osteosarcoma? 
The lungs are the preferential site for metastases in patients with osteosarcoma (good thing we did a chest x-ray).

Most cells in this image are malignant mesenchymal cells that have produced spicules of mineralized bone surrounded by osteoid matrix (must be osteoblastic in origin). The production of osteoid matrix by the tumor cells is characteristic of osteosarcomas.

What tumor is characterized by malignant neoplastic cells producing a cartilaginous matrix? 

Chondrosarcoma is characterized by malignant neoplastic cells producing a cartilaginous matrix.

Is osteosarcoma a familial tumor? 
Patients who are born with a germline mutation of the RB gene are predisposed not only to retinoblastoma, but also to osteosarcomas. Most osteosarcomas are not familial, however; there is no increased risk for siblings (having a family member who have a bone cancer at 80+ does not increase the risk).

In this example, an osteosarcoma has arisen from the scapula of a 63-year-old woman who was treated with radiation for primary carcinoma of the breast.

Histologic section from the tumor shown in Image 4 illustrates neoplastic cells forming osteoid.

Is this tumor a primary or secondary osteosarcoma? 

This is a secondary osteosarcoma. (Can’t differentiate from the slide, but it’s an osteoid producing neoplasm found in the lung)

Chondrosarcomas are about one half as frequent as osteosarcomas. The tumor has developed in the proximal femur, and it has not destroyed the cortex. The tumor has a bluish, glassy appearance, reminiscent of cartilage. Compare and contrast the location, incidence, age of occurrence, and histology of chondrosarcoma with primary osteosarcoma

This is an example of a chondrosarcoma. The malignant neoplastic cells produce a chondroid matrix in which they become embedded. Distinguishing benign and malignant cartilaginous lesions histologically is often difficult. The radiologic impression and the presence of invasion of the surrounding bone are often crucial factors in making this distinction.

At what age do patients develop chondrosarcoma, and which anatomic sites in the skeleton are affected? 

Patients with chondrosarcoma are older than patients with primary osteosarcoma; the mean age for chondrosarcoma is 43 years. The most frequent locations are in the pelvis, proximal femur, ribs, sternum, and shoulder girdle. It is the most common malignant tumor of the scapula and sternum. (Chondrosarcoma is half as likely as primary osteosarcoma, but seen in 2X older population, doesn’t predominate around the knee)

In this image, note the large neoplastic mesenchymal cells with hyperchromatic nuclei embedded in a cartilaginous matrix. In low-grade tumors, the malignant cells are smaller, are less hyperchromatic, and closely resemble normal chondrocytes

Why is it important for the pathologist to grade chondrosarcomas? 

There is a direct correlation between the grade and the biologic behavior of the tumor. Metastasis from grade 1 tumors is rare, whereas metastasis from grade 3 tumors is likely. When chondrosarcomas metastasize, they preferentially spread to the lungs (like osteosarcomas)

This is a classic example of giant cell tumor of bone. The lesion has arisen in the epiphysis and grown to produce a clublike expansion of the distal end of the radius (golf club like). The cortex has not been destroyed by the tumor; rather, it has remodeled to accommodate the expanding mass. These tumors are believed to arise from a monocyte precursor (unlike osteosarcoma or chondrosarcoma)

What are the most common age and sex of a patient with giant cell tumor of bone? 

Giant cell tumors usually arise in patients 25 to 45 years old, and there is a slight female predominance.

In the radiograph, you can see that the tumor is located within the epiphysis. In addition, the tumor destroys bone, and it appears that the tumor is cystic. Radiologists describe this feature as a "soap bubble" lesion. The cortex is thin, but not destroyed. Contrast this finding to that seen in osteosarcomas.( origin and cystic nature sound like osteoclastic in nature)

This image is another example of a giant cell tumor of bone. There is an expansive mass surrounded by a remodeled cortex. In this example, note the hemorrhage, a common finding in giant cell tumors of bone.

Histologically, the tumor consists of sheets of small mononuclear cells admixed with numerous giant cells. The mononuclear cells are the neoplastic cell population. Although this tumor is histologically benign, 2% of giant cell tumors metastasize to the lungs after surgery. (same site as osteosarcoma, chondrosarcoma)

We have examined three primary tumors of bone. Metastatic cancer to bone is more common than primary malignant tumors of bone. Metastatic tumors can produce either an osteolytic or an osteoblastic reaction in the bone. Classically, prostatic adenocarcinoma produces osteoblastic foci. This is thought to be partly due to overexpression of urokinase-type plasminogen activator (u-PA) and prostate-specific antigen (PSA), a serine protease that may block tumor-induced bone resorption and activate osteoblast growth factors.

At higher magnification, islands of prostatic adenocarcinoma can be seen adjacent to the bony spicules (contrast with osteosarcoma)

The patient is a 2-year-old white girl who reportedly fell from a car on March 19. She was examined in a local emergency department, and radiographs of her skull were performed. She was found to have no fractures and was discharged. She did ambulate after the accident, but on March 27, she was noted to have difficulty in walking. She was seen by her pediatrician; otitis media was diagnosed, and antibiotic treatment was begun.

The difficulties with walking worsened, and she was referred to an orthopedist on April 4. Radiographs showed some periosteal reaction consistent with a fracture of the distal femur, and she was placed in a long-leg cast. She was taken out of the cast on May 24. At that time, the fracture was healed, and the patient was allowed to ambulate with full weight bearing.

She did well until July 26, when a soft tissue mass appeared over the lateral aspect of the distal femur. At this time, she was ambulating without difficulty, and was not systemically ill. X-rays showed aradiolucency in the distal femur, and she was referred to an orthopedic surgeon. At this office, x-rays showed lateral and posterior soft tissue swelling around the distal femur, matured periosteal bone, and a radiolucency in the distal femoral metaphysis that appeared to extend down to or perhaps through the physis. MRI confirmed a fluid-filled radiolucency in the distal femur that communicated with the soft tissues through a posterior perforation of the distal femur. An open biopsy was performed, and tissues were sent for histopathologic examination. Exploration of the femur revealed that the cavity extended through the physis into a portion of the epiphysis. The postoperative plan was for 6 weeks of intravenous antibiotics and for close follow-up with serial radiographs to assess for possible growth arrest.

Osteomyelitis

In this radiograph, a lytic lesion can be seen in the distal metaphysis of the femur.

Why is this lesion in the metaphysis? 

The location of the lesion depends on the route by which bacteria gain access to the bone. The most common route is hematogenous. The metaphysis is quite vascular, and is often the site where infection localizes.

This image shows a specimen curetted at surgery. There is a fragment of mineralized debris surrounded by numerous acute inflammatory cells. The vessels are congested. This is the classic histologic presentation of acute osteomyelitis.

With higher magnification, it is clear that the infiltrating cells are predominately neutrophils.

What organism would you expect to culture from a pyogenic osteomyelitis? 

Staphylococcus aureus is the most common organism isolated from hematogenously spread osteomyelitis. The specific pathogen in this patient was not determined.

In the center of the field is a bone fragment that is surrounded by a mononuclear cell infiltrate. There are only a few neutrophils. The dead bone must be removed before the lesion can resolve. Osteoclasts may not survive in the inflammatory milieu, so the necrotic bone must be removed surgically.

What is the significance of the empty lacunae in the bone fragment? 
Empty lacunae are a histologic hallmark of necrosis of bone.

This photograph is not from the patient in Case 4, but is from a patient with chronic osteomyelitis of the midshaft of the tibia. A large fragment of necrotic cortex is visible deep within the draining sinus. This necrotic bone is called the sequestrum. The reactive periosteum has formed a collar of reactive bone around the chronic draining lesion. The reactive bone is called the involucrum.

A 40-year-old white woman presented to her physician with vague complaints of fatigue, anorexia, and generalized weakness for the previous 6 months. She complained that it was difficult to ambulate on rising from bed (morning stiffness), but after about 30 minutes she felt better and was able to move about the house. She also complained that stiffness and pain in her wrists and fingers made it difficult to do routine chores in the kitchen because her manual dexterity was compromised. She was especially concerned about the recent swelling in the joints of her fingers (more than three joints involved; symmetric involvement).

On physical examination, her knees were swollen and tender, and motion in her knees and hips was limited. Her knees and both wrist joints were warm, but with no erythema. The proximal interphalangeal joints of both hands were warm and enlarged by nonbony fusiform swelling (inflammatory problem?). She had two small, nonpainful, subcutaneous (soft tissue) nodules along the proximal ulna of her left arm. Radiographs of affected joints indicated soft tissue swelling, joint effusion, and juxta-articular osteopenia. Synovial fluid was aspirated and had the following characteristics:

Viscosity - low
Color - translucent, yellow
White blood cells - 3000 cells permm³ with 50% neutrophils
No crystals
Bacterial culture - negative

The patient had the following clinical pathologic features:

HLA-DR4 - positive
Rheumatoid factor - positive at a titer of 1:500
Erythrocyte sedimentation rate - increased

Serum cyclic citrullinated protein (CCP) antibodies - positive

The patient expressed concern that she may have the same disease as her sister, who became so incapacitated with arthritis that she had to have her right hip replaced with a prosthesis. She asked the physician to review her sister's medical history to determine if they had the same disease.

Medical records were available for her sister's first consultation only.

At the time of her first examination, she was a 40-year-old obese white woman with deep, achy, poorly localized pain in the region of her right hip and in her knee. She reported that, over the prior 2 months, she had had difficulty getting out of bed because her knee and hip were stiff and sore. Even after she had been up and mobile for several hours, the symptoms persisted. On physical examination, motility of her hip joint was found to be reduced. She felt well except for the pain in her hip. She had bony, nonpainful swellings along the medial aspect of two distal interphalangeal (DIP) joints of each hand. Her erythrocyte sedimentation rate was normal. Synovial fluid was aspirated and had the following features:

Viscosity - normal
Color - translucent, clear
White blood cells - <200 cells/mm³ with <5% neutrophils
No crystals

The patient had the following clinical pathologic features:

Rheumatoid factor - negative
Erythrocyte sedimentation rate - normal

Serum CCP antibodies - negative

Radiographs of her hip joints revealed narrowing of the joint space, subchondral bone sclerosis, subchondral cysts, and osteophytes. A referral letter in the chart, dated 10 years after the first examination for arthritic disease, indicated that her right femoral head had been replaced with a prosthesis.

This is a classic presentation of acute rheumatoid arthritis. It is polyarthritic, affects the proximal interphalangeal joints, and has produced a fusiform swelling of the soft tissue. The lesion is usually symmetric.

How does the distribution of affected joints in the hand differ from that seen in degenerative joint disease? 
The lesions of degenerative joint disease in the hand are found in the distal interphalangeal joints, are bony, and are not symmetric

In this case, there is marked destruction of the epiphyseal bone. The joint spaces are narrowed because of the destruction of the articular cartilage. In severe cases, the joints become fused by bony ankylosis.

What is the significance of the radiologic findings in rheumatoid arthritis (RA)? 
In RA, there is diffuse narrowing of the joint space. Activation of CD4+ T cells results in a cytokine milieu that causes recruitment of additional inflammatory cells and a destructive proliferative synovitis. Proliferation of the synovial membrane leads to pannus formation, which isolates the cartilage from the synovial fluid, its source of nutrients. The severe, extensive damage of RA often leads to ankylosis. In chronic RA, the periarticular bone is osteoporotic, a change secondary to disuse of the affected limbs, to the stimulation of osteoclasts by corticosteroid therapy, or to the release of RANK-L by activated lymphocytes in the synovium.

This specimen illustrates the inflamed synovium characteristic of acute rheumatoid arthritis. Note the prominent, hyperemic synovial membrane on which strands of fibrin are evident.  (Middle section; fibrin products seen near dead center)

List two important histologic changes found in the synovial membrane in joints affected by rheumatoid arthritis. 

The synovium is proliferative (destructive and proliferative) and is infiltrated by numerous lymphocytes and plasma cells.

This image emphasizes the inflammatory nature of rheumatoid arthritis. In this section of reactive synovium, lymphocytes, plasma cells, and macrophages expand the synovium. The vascularity is increased. The synovial membrane is also hyperplastic. The inflammatory infiltrate may organize into distinct lymphoid nodules.

Which class of lymphocytes predominates in the inflammatory infiltrate? 
An autoimmune reaction in which T cells play the pivotal role accounts for the inflammation and joint destruction. CD4+ cells accumulate in affected joints, where they stimulate monocyte-macrophages to release cytokines and recruit B cells, which produce antibody—most importantly, the autoantibody rheumatoid factor (IgM against the Fc portion of IgG). During active inflammation, the synovial tissue generates a plethora of cytokines and growth factors. It is now generally accepted that IL-1 and TNF are key mediators in the cytokine cascade.

This is a higher magnification of the previous image. The reactive synovium is clearly evident. The inflammatory cells are organized into a lymphoid nodule. The primary lesion of rheumatoid arthritis is synovitis.

What is the pannus? 
The pannus consists of the inflamed, hyperplastic synovium that extends over the articular surface.

What is the significance of the clinical signs of anorexia, fatigue, and generalized weakness in the first patient? 
Rheumatoid arthritis (RA) is a chronic, relapsing, inflammatory disease that includes the joints. Although the principal target is the synovial lining of joints, the disease also affects many organ systems—skin, heart, lungs, blood vessels, and muscle. The release of inflammatory cytokines, such as IL-1 and TNF, from the joints into the circulation can lead to the generalized systemic signs and symptoms noted in this case. Also, 80% of individuals with RA have autoantibodies (usually IgM) to the Fc portion of IgG. These circulating complexes contribute to the extra-articular signs of RA. Anti-CCP antibodies have also been identified more recently as a relatively specific marker for RA.(likely anemia of chronic disease)

RANK-L, released from the surface of lymphocytes by metalloproteinases, stimulates osteoclastogenesis. The osteoclasts are important players in the destruction of the subchondral bone in rheumatoid arthritis. Inflammatory mediators released from the pannus stimulate osteoclast activity, which results in erosion and destruction of the subchondral bone. The pannus isolates the articular cartilage from the synovial fluid, resulting in degeneration of articular cartilage

What is the significance of finding inflammatory cells in the joint fluid?
Quantitation of white blood cells is an important part of synovial fluid analysis, especially because it is the major basis for classification of an effusion as septic, inflammatory, or noninflammatory. See Table above.

This image illustrates the destructive nature of chronic, severe rheumatoid arthritis. Subluxation and fusion of joints is apparent. Ulnar deviation of the digits is common. The lesion is polyarticular and symmetric. The most common deformity of the thumb is flexion (Z-thumb) with hyperextension at the interphalangeal joint (Swan necking).

How does RANK-L contribute to the destruction of the joint? 
RANK-L is released from activated lymphocytes in the synovium stimulating the proliferation of osteoclasts. Osteoclasts rapidly erode the subchondral bone.

Rheumatoid nodules consist of a central zone of fibrinoid necrosis surrounded by a prominent rim of epithelioid histiocytes and numerous lymphocytes and plasma cells (part of chronic RA). Rheumatoid nodules occur in approximately 20% to 25% of patients with definitive or classic rheumatoid arthritis. Nodules generally are associated with severe articular and systemic disease and with high titers of rheumatoid factor.

Where do rheumatoid nodules typically develop? 
The nodules typically appear on the extensor surface of the forearm below the elbow, or at sites of local pressure, such as the Achilles tendon. Less commonly, they form in the lungs, spleen, myocardium, and heart valves. The subcutaneous nodules are firm, nontender, and round to oval.

Degenerative joint disease is most common in the large, weight-bearing joints—hips, knees, and vertebrae. The exception to this rule is the distal interphalangeal joint, where degenerative joint disease is common, even though the joint is not large, and it does not bear weight. In this image, the knee joint has been opened anteriorly under the patella. For orientation, the hip is to the right, and the foot is to the left. There has been extensive destruction of the articular cartilage of the lower end of the femur. The synovium is not hyperplastic, and it is not inflamed. There is no evidence of pannus.

A common finding in degenerative joint disease is the formation of osteophytes at the margin of affected joints. In this image, three osteophytes/Heberden nodules are projecting from the intervertebral joints.

Osteoarthritis of the hip is common. In this typical image, there is marked irregularity and erosion of the articular surface. Very little articular cartilage remains.

In more advanced cases, no cartilage remains, and apposing bones rub together, resulting in eburnation of the bone. Grossly, eburnated bone is shiny and smooth. Histologically, it is sclerotic.

Gout is an inflammatory disease. This image illustrates a classic case of acute gout (podagra). The first metatarsophalangeal joint is the site most commonly affected. It is swollen, red, and, no doubt, very painful. Sodium urate crystals have precipitated into the joint, producing an acute inflammatory response.

What would be the characteristic feature of joint fluid aspirated from the affected joint? 
The fluid would contain large numbers of neutrophils, and long, needle-like, sodium urate crystals.

This is an example of chronic gout with gouty tophi. There are numerous asymmetric, periarticular swellings. These represent inflammatory reaction to sodium urate crystals. The lesion on the fifth digit of the left hand has ulcerated, revealing the white crystals. Tophi appear only after repeated attacks of gout in patients whose hyperuricemia has not been treated.

Besides joints, what other organ is affected in gout?
In patients with chronic gout, the kidney can be severely damaged; approximately 20% of patients die of renal failure. Renal lesions are many: precipitation of urates in the medulla forms tophi; uric acid stones may form; and in some cases, there is acute renal failure owing to precipitation of urates in the collecting tubes.

Histologically, tophi consist of crystals that are surrounded by macrophages, lymphocytes, and often foreign body giant cells. In routinely processed sections, the crystals are dissolved during processing.

How does this lesion differ from a rheumatoid nodule? 
The center of a rheumatoid nodule consists of fibrinoid necrosis, rather than urate crystals.

A 12-year-old girl came to the emergency department with fatigue, weight loss, polydipsia, polyuria, vomiting, and drowsiness. On examination, she was found to have a blood pressure of 90/55 mm Hg, a pulse rate of 110 beats/min, cold extremities, and deep, sighing respirations (Kussmaul respiration).

Laboratory investigation at initial presentation:

After management of this acute episode, the patient was treated with twice-daily insulin therapy.

Twenty-five years later, at age 37, the patient presented to the emergency department with acute substernal chest pain that radiated to her neck and down her left arm. This pain lasted for at least 30 minutes, and was associated with nausea and sweating. Investigations done at this time revealed that her serum markers of myocardial injury were increased. Her CK-MB was 25 ng/mL (reference range 0-3 ng/mL), her total CK was 500 U/L (reference range 38-120 U/L), and her troponin I was 9.4 ng/mL (reference range <0.5 ng/mL). An electrocardiogram revealed evidence of a myocardial infarction (ST segment changes and Q waves). After a 7-day stay in the hospital, she was discharged and asked to continue insulin therapy. (bold is MI cardiac enzyme)

She was lost to follow-up, but presented 2 years later with generalized edema. On physical examination, there was no clinical evidence of cardiac failure. Neurologic examination revealed muscle weakness and loss of sensation in both lower extremities (peripheral neuropathy). She also had bilateral visual impairment. Examination of her retinas with an ophthalmoscope revealed microaneurysms in retinal vessels. All of her peripheral pulses were palpable. Laboratory tests revealed elevations of blood urea nitrogen and serum creatinine (both indicating renal failure). Urine examination revealed glucose 2+ and massive proteinuria.

Involvement of large and small blood vessels is very characteristic of long-standing diabetes. In large blood vessels such as the one shown here, there can be severe and extensive atherosclerosis. This change occurs earlier in diabetics than in nondiabetics.  Note the plaques of ulceration and thrombus imposed within the normal vasculature.

What are important clinical consequences of premature and severe atherosclerosis in diabetics? 
Clinical consequences include peripheral vascular disease, aortic aneurysm (Goljan doesn’t think there is an increase, but worse prognosis if it occurs), myocardial and gastrointestinal ischemia, and stroke.

The retina provides an opportunity to visualize the small blood vessels directly. Diabetics have a constellation of changes in their retinas, collectively termed diabetic retinopathy. This funduscopic image shows a large, pale area of edema around the central avascular macula (look at the bulging of the optic disc; must be some increased vessel permeability). There are numerous small new blood vessels at the periphery of this zone (neovascularization via VEGF) and several hemorrhagic foci (darker areas).

What is the pathogenesis of this change? 
Ischemia due to microangiopathy and atherosclerotic vascular compromise serves as a stimulus for neovascular proliferation. These abnormal small vessels are prone to hemorrhage.

What other changes may be seen in the retina? 
Other changes that may be seen in the retina include exudates, atheroemboli from aortic or carotid plaques (Goljan doesn’t think there is an increased risk, but worse prognosis if it occurs), hemorrhagic retinal detachment, and microaneurysms.

What are the other ocular complications of diabetes? 
Cataracts, glaucoma, decreased visual acuity, and blindness are the other ocular complications of diabetes.

Kidneys are often severely affected in diabetes. Kidney problems result from vascular disease affecting the large blood vessels and glomerular capillaries, and from increased predisposition to infections. The gross appearance of the kidney varies, depending on the type of vascular lesion. Typically, as seen here, kidneys with diabetic glomerulosclerosis show diffuse, fine granularity of the cortical surface, resulting from destruction and scarring of the glomeruli.

What are long-term complications of diabetes mellitus? 

1. Diabetes affects blood vessels of all sizes. Accelerated atherosclerosis (macroangiopathy) affects all of the usual sites—aorta, carotid arteries, peripheral arteries, and coronary arteries. Microangiopathy, or small vessel disease, affects capillaries throughout the body, but important clinical effects are seen in the kidney and eyes. Diabetics have a 100-fold increase in atherosclerotic narrowing of medium-sized arteries such as the femoral and popliteal, and attendant increase in gangrene. Review: Cell Injury Introductory Images, Image 18 (foot, dry gangrene, clinical presentation)

2. Diabetic patients are also more susceptible to infections, and infections increase insulin requirements; in type 1 diabetics, infections can precipitate ketoacidosis.

3. Neuropathy is another long-term complication of diabetes.

Which complications did this patient have at the time of her second admission? 
This patient, at the time of her second admission, had coronary atherosclerosis (rare in a 37-year-old nondiabetic woman) with myocardial infarction and renal insufficiency, resulting from diabetic nephropathy.

Kidneys are frequently affected in diabetes mellitus. This low-power view shows hyaline thickening of the arterial wall and evidence of tubular destruction, seen as an increase in the interstitial fibrous tissue. One of the glomeruli in this field has been totally replaced by scar tissue, and hence, it appears acellular and hyalinized. The two other glomeruli show nodular glomerulosclerosis, seen better at a higher magnification in the next image.

What type of diabetes does this patient have? 
This patient has type I diabetes; she presented at a young age with diabetic ketoacidosis.

What is the pathogenesis of type 1 versus. type 2 diabetes? 
Type 1 diabetes is an autoimmune disease resulting in destruction of beta cells in the pancreatic islets. The autoimmune response is probably triggered by some unidentified environmental agent (e.g., virus, chemical, toxin). In genetically predisposed individuals, beta cell injury leads to autoimmunity. At least one gene that regulates this phenomenon is linked to the HLA-D region. The importance of an environmental trigger is underscored by the fact that even in identical twins, the concordance rate of type 1 diabetes is only 50%. Type 2, or non-insulin-dependent, diabetes is genetically and biochemically distinct from type 1 diabetes. Although there is a strong genetic predisposition, there is no evidence of autoimmunity or HLA linkage. It usually starts in adults (>30 years old), and 80% of the patients are obese. The deficiency of insulin is mild relative to that of type 1 diabetes, and the major factor, at least at the onset, seems to be insulin resistance (i.e., the target tissues are resistant to the action of insulin).

Various glomerular lesions may occur in diabetes mellitus. Nodular glomerulosclerosis, very characteristic of diabetes, is seen here. There is deposition of pink-staining material in the mesangial core of the glomeruli. This material appears in the form of nodules seen at the periphery of the glomerular capillary tufts. The nodules contain mesangial matrix material. In addition to nodular glomerulosclerosis, the glomeruli also show diffuse thickening of the basement membrane and a diffuse increase in the mesangial matrix.

What is the pathogenesis of these changes? 
The pathogenesis of diabetic nephropathy is complex and involves progressive glomerular hyperfiltration, nonenzymatic glycosylation of proteins, and a deranged cytokine milieu.

What are the clinical consequences? 
Clinical consequences include proteinuria and eventual renal failure

The PAS stain highlights the glycoprotein-rich basement membrane in Bowman capsule and the mesangial nodules.

What are the clinical consequences of the glomerular changes in diabetic nephropathy? 
Clinical consequences of glomerular changes include proteinuria and a progressive decrease in the glomerular filtration rate.

What is the biochemical basis of diabetic ketoacidosis? 
1. Shift in the hormonal balance in favor of the counterregulatory hormones—glucagon, epinephrine, growth hormone, and cortisol—over insulin, often resulting from some form of stress.

2. Hyperglycemia results from decreased glucose uptake by tissues and increased gluconeogenesis and glycogenolysis.

3. Hyperglycemia induces an osmotic diuresis, which results in fluid and electrolyte loss.

4. Ketogenesis increases because of increased lipolysis triggered by the counterregulatory hormones.

5. The free fatty acids that are released can be converted in the liver to ketone bodies.

6. Increased ketone bodies result in a metabolic acidosis, manifested as low pH and low bicarbonate, which is consumed in buffering the keto acids.

7. The metabolic acidosis stimulates the respiratory center to reduce the Pco₂ to correct the acid-base disturbance; the resulting increased respiration, which is classic, is a deep, sighing respiration (Kaussmal respirations), which reduces the Pco₂.

This low-power view shows pancreatic acini, stroma with blood vessels, and a few islets of Langerhans. The exocrine part of the pancreas is normal. The changes in the islets are seen better on higher magnification in the next image.

In this high-power view, an islet surrounded by normal pancreatic acini is seen. The islet shows extensive deposition of a pink homogeneous material that has the features of amyloid. This change is often, but not always, seen in long-standing type 2 diabetes.

What is the chemical composition of amyloid in this particular setting? 
Amyloid comprises amylin molecules, a peptide cosecreted with insulin from beta cells.
Very Rarely seen in T1DM

What effect may the amyloid have on the function of the islets? 
Amylin oligomers disrupt cell membranes and may contribute to islet cell loss.

A 42-year-old man, previously in good health, presented to his physician for evaluation of headache and "problems seeing." The patient stated that over the past year, he had developed headaches that were generally worse while reclining. Although aspirin or acetaminophen had provided symptomatic relief during the first 6 months, his pain had become more persistent over the last 6 months. In addition, over the last 6 months, the patient had noted the development of "blind spots" in his lateral fields of vision, particularly on the right side. Physical examination revealed slight blurring of the optic disks. An asymmetric bitemporal visual field deficit was present, involving the right temporal visual field more than the left.

CT and MRI scans of the head revealed a large midline mass associated with erosion of the sella turcica (Image 1). The mass extended into the suprasellar space and into the right cavernous sinus. Laboratory evaluation revealed a prolactin level of 90 ng/mL (normal < 14 ng/mL). The patient was taken to the operating room, where the sellar mass was exposed via frontotemporal craniotomy. The mass obliterated the diaphragma sella and the lateral walls of the sella turcica; it compressed the optic chiasm superiorly and extended bilaterally into the cavernous sinuses. A small biopsy specimen of the mass consisted of soft, almost gelatinous, tan tissue. Histologic examination of the specimen revealed a monomorphous population of cells with uniform, round-to-ovoid nuclei and amphophilic cytoplasm (Images 2 and 3). The mass was resected as completely as possible. The patient made an uneventful postoperative recovery and was discharged, to be followed in neurosurgery and endocrinology clinics.

This MRI demonstrates a large lesion involving the sellar and suprasellar regions. The patient has been injected with contrast material, which causes this particular mass to enhance as a bright (white) lesion. Compare this image to the coronal section of the pituitary adenoma in Image 6 in this case.

What additional studies might be done to further characterize this patient's tumor? 
Other studies that might be done include immunohistochemical staining for the anterior pituitary hormones. An immunostain for prolactin, in particular, is probably the most significant one in this case. A negative prolactin stain would confirm that the elevated prolactin level was due to stalk effect, rather than secretion of hormone by the neoplasm. If prolactin was present within the neoplasm, however, postoperative treatment with bromocriptine (a dopamine agonist that inhibits prolactin secretion and shrinks prolactin-producing cells) might also be indicated.

Note the monomorphic cellular proliferation. The cells are growing in a diffuse pattern, and lack the characteristic nesting architecture of the normal anterior pituitary gland. For comparison, review the microscopic features of the normal anterior pituitary gland in Image 7.

At higher magnification, the comparatively uniform, amphophilic (amphophilic means that the color is somewhere in no-man's-land between eosinophilic and basophilic) staining pattern of the neoplastic cells is apparent. This monotony contrasts with the mixed cell population seen in the normal anterior pituitary gland.

What is your diagnosis in this case? 
Pituitary adenoma.

What processes need to be considered in the differential diagnosis of the patient's sellar mass? 
The differential diagnosis of sellar-region masses would include pituitary adenomas of all flavors, tumors of the meninges, and primary suprasellar neoplasms (e.g., craniopharyngioma, germ cell tumor, and pilocytic astrocytoma). The presence of extensive sellar erosion in this case weighs against a primary suprasellar lesion, but does not completely exclude it from consideration. Endocrine evaluation and surgical exploration are usually necessary to make the definitive diagnosis.

What additional studies might be done to characterize this patient's tumor further? 
A histochemical stain for reticulin is useful to highlight the lack of a connective tissue framework as would be present in normal pituitary tissue. In addition, immunohistochemical stains for neuroendocrine markers would confirm the derivation of this tumor. Immunohistochemical staining for the various anterior pituitary hormones may correlate with the functional status of the tumor.

This specimen shows a pituitary adenoma discovered incidentally in a patient who died of unrelated causes. Pay special attention to the relationship between the adenoma and adjacent structures to understand better some of the presenting clinical manifestations of mass lesions in the pituitary region. The right olfactory nerve is pointing at the tumor. The adenoma has been removed en bloc with the brain; it is invested superiorly by the diaphragma sella, a portion of which is visible anterior to the tumor. Note the proximity of the tumor to the optic nerves.

How would you explain the patient's visual field deficits? Why are the deficits present in a bitemporal distribution? 
The patient's visual field deficits are caused by expansion of the sella-region mass superiorly, resulting in compression of the optic chiasm at the base of the brain. The temporal visual fields are visualized via activity of the medial (nasal) areas of the retina. Fibers emanating from the medial retina decussate (cross) at the optic chiasm. If the chiasm is compressed, these decussating fibers are compromised, resulting in loss of images from the medial retina in both eyes and a bitemporal field cut. In real life, this is often a bit asymmetric, as in this patient. The medial (nasal) visual fields are visualized by the temporal area of the retina, whose fibers do not decussate.

The pituitary adenoma has been removed to show local changes caused by the mass effect of the tumor. Note the depressed area just anterior to the mammillary bodies, which marks the site of the adenoma. As noted in the previous image, as pituitary adenomas expand, compression of the visual pathways and resultant visual field deficits are common. Textbooks frequently mention a bitemporal hemianopsia, as was present in our patient, occurring because of compression of fibers in the optic chiasm coming from the nasal aspect of the retina. In practice, the visual field deficits may be quite variable. If untreated, pituitary adenomas may grow far beyond the immediate vicinity of the sella, as is illustrated in the next image.

What is the cause of the patient's elevated prolactin level? 
The mildly elevated prolactin level is a common phenomenon, related to the so-called stalk effect, rather than to direct secretion of prolactin by the tumor. Any mass in this site can cause a mild elevation in prolactin by interfering mechanically with hypothalamic-hypophyseal connections and disrupting the steady-state inhibitory effect of the hypothalamus on prolactin secretion by the anterior pituitary gland. Mild hyperprolactinemia in the presence of a mass in the pituitary region does not justify a diagnosis of a prolactin-secreting pituitary adenoma. Patients with functional prolactinomas generally have a serum prolactin level greater than 200 ng/mL.

What other endocrine studies might be useful in this patient? 
Other endocrine studies might include assays of the other anterior pituitary hormones (GH, TSH, ACTH, LH, FSH). Pituitary adenomas may be associated with secretion of excessive amounts of these hormones, singly or in combination. In contrast, nonsecretory adenomas may compromise the native anterior pituitary gland sufficiently to produce hypopituitarism.

This specimen shows an advanced pituitary adenoma, similar to the scan in Image 1. This lesion was from an elderly woman who presented for evaluation of weakness and altered mental status, and it is comparable in size to the one noted in the imaging studies from our patient. The adenoma has grown far beyond the confines of the sella turcica, has markedly distorted the left lateral ventricle, and encases the internal carotid artery. The neoplasm contains several small areas of hemorrhage. In some cases, pituitary adenomas may undergo extensive spontaneous hemorrhage, causing a substantial rapid increase in the size of the mass. Ancillary studies in this autopsy case revealed no evidence of hormone production by this adenoma.

Why would nonfunctional pituitary adenomas (i.e., adenomas that do not secrete an active hormonal product) typically be larger than hormonally active tumors at the time of diagnosis? 
Nonfunctional tumors come to clinical attention only by mass effects or panhypopituitarism, whereas small functioning tumors produce enough hormone to produce typical end-organ effects that suggest the diagnosis.

This image illustrates the normal constituents of the anterior pituitary gland. Note the mixture of cell types, including the red-staining acidophils, the purple-staining basophils, and the chromophobes, whose cytoplasm stains only weakly. The variability in staining reflects the presence of different hormonal secretory products (prolactin or growth hormone in acidophils; TSH, ACTH, or gonadotropins in basophils). Immunohistochemical staining, shown in the next image, may be used to identify the hormone secreted by a given cell. The cells are grouped into small nests by the normal connective tissue framework of the anterior pituitary gland.

In this section, somatotropic (human growth hormone–secreting) cells have been labeled with an antibody to human growth hormone. The antibody has been linked to a chromogen that stains the somatotropic cells brown.

What molecular lesions have been documented in pituitary adenomas? 
Pituitary tumor transforming gene (PTTG) encodes a protein that is overexpressed in most pituitary adenomas. This protein plays a role in cell cycle regulation and DNA repair, and is overexpressed in various other neuroendocrine and non-neuroendocrine tumors. The degree of PTTG overexpression in pituitary adenomas has been found to correlate with aggressiveness and biologic behavior. Clonal mutations in some adenomas affect the G protein, Gs. About 40% of GH-secreting tumors have a single base-pair missense mutation in the alpha subunit of Gs, converting it into the oncogene GSP, which stabilizes the G protein in its active conformation by inhibiting GTPase activity. This activity mimics the stimulatory effect of specific extracellular growth factors and makes the adenoma less responsive to feedback inhibition.

Craniopharyngioma is thought to be derived from vestigial remnants of Rathke's pouch. Affected patients may be adults or children. The tumor may be intrasellar, although most are suprasellar, and may come to clinical attention because of hormonal deficiencies or visual disturbances. Histologic features include keratinizing squamous cells, calcifications, cholesterol crystals, fibrosis, chronic inflammation, gliosis, and a peripheral layer of columnar cells.

A 28-year-old woman noticed, while attempting to button her shirt collar, that her neck was enlarged. She had not gained weight; rather, she had lost a small amount of weight despite having avoracious appetite. She felt well and active; whereas she formerly had constipation, she now noted that she had bowel movements twice daily. On physical examination, her pulse was 86 beats/min, and her blood pressure 125/70 mm Hg.

On visual inspection, she appeared to have a wide-eyed stare with a slight lagging of the upper lidon slow downward gaze. Her thyroid gland was asymmetrically enlarged with a firm 1.5-cm nodulein the middle of the left lobe and was estimated to weigh 40 g. The initial impression was moderate thyrotoxicosis with a single, prominent, goitrous nodule. Although the lid retraction suggested increased sensitization of the adrenergic system, the absence of proptosis (protrusion of the globe) indicated absence of significant clinical autoimmune ophthalmopathy at this time.

Laboratory data included fasting glucose 105 mg/dL, free T₄ 2.2 ng/dL (reference range 0.76-1.8 ng/dL), and TSH zero (undetectable) by a highly sensitive assay. A radioiodine scan was performed. Her thyroid gland had a marked, diffuse uptake, well beyond the upper limits of normal. The left lobe had an area of decreased functional uptake corresponding to the palpable nodule. Fine needle aspiration biopsy of the left lobe was performed, which revealed papillary clusters of epithelial cells with enlarged, "powdery" nuclei and several psammoma bodies. Surgical treatment was suggested to treat her illness.

Surgical treatment was suggested to treat her illness.

This thyroid gland is symmetrically moderately enlarged and would show beefy red parenchyma on cut sections.

What are other causes of thyroid gland enlargement? 
Goiter, early Hashimoto thyroiditis, and neoplasms are other causes of thyroid gland enlargement.

How do T₄ and T₃ interact with target cells? 
Unbound T₄ and T₃ enter cells in many tissues and bind nuclear receptors, changing gene expression to increase carbohydrate and lipid catabolism and stimulate protein synthesis, increasing the basal metabolic rate.

Thyroid parenchymal lobules are separated by thin, fibrous septa. The gland shows diffuse hyperplasia, which is not uniform in all areas (note sparing in the lower left corner of the image). Hyperplastic papillary infoldings replace much of the luminal colloid in the follicles in this image. There may be a patchy lymphoid infiltrate (not pictured), which may include rare germinal centers and prominent vascularity.

What are other causes of thyroid gland hyperplasia? 
Other causes of thyroid gland hyperplasia include thyroid-stimulating hormone–producing pituitary adenoma (rare) and goiter (hyperplasia is patchy).

Is thyroid gland hyperplasia always associated with hyperthyroidism? 
No. In many patients, goiter develops in response to some factor that limits the synthesis of T₃ and T₄. Such compensatory hyperplasia is a response to thyroid-stimulating hormone stimulation, and the patient is generally euthyroid and may even be hypothyroid.

What are other causes of hyperthyroidism? 
Other causes of hyperthyroidism include an adenoma that secretes thyroxine (toxic adenoma), a hyperactive nodule in a goiter (toxic goiter), and excess exogenous hormone intake. Toxic adenoma and toxic goiter would show a different thyroid scan than this patient's—a hot nodule and relatively low uptake in the rest of the gland.

How do the papillary infoldings of Graves disease compare and contrast with papillae of papillary thyroid cancer? 
The papillae in Graves disease are generally within a follicle, are small, have preserved nuclear polarity, and are present diffusely in the gland. The nuclear characteristics of papillary carcinoma (chromatin clearing, pseudoinclusions, grooves) are diagnostic of this entity and not seen in Graves disease. In addition, the papillae in papillary carcinoma are localized to the tumor, are usually larger, and frequently have a more prominent fibrovascular core.

What is the stimulus to hyperfunction in Graves disease? 
Autoantibodies bound to TSH receptors on the cell membranes provide the stimulus. There is a strong association between Graves disease and HLA-B8 and HLA-DR3.

What is the most important screening test to determine the functional status of the thyroid gland? 
A sensitive TSH (thyroid-stimulating hormone, thyrotropin) assay is the best screening test because the TSH level is exquisitely tuned to the level of free T₄. In the absence of pituitary disease, TSH levels are elevated in patients with hypothyroidism and close to zero in patients with hyperthyroidism.

Radioactive iodine is concentrated from the blood by thyroid follicular cells, allowing correlation of anatomic features with thyroid function. Decay of radioactive iodine is detected as dark spots on the scan. A normal thyroid gland shows diffuse moderate iodine uptake in the right and left lobes and isthmus. Graves disease is characterized by diffuse increased uptake. Multinodular goiter most often shows patchy, irregular uptake with some nodules hyperfunctional compared with normal (dark, or "warm," on scan) and other nodules hypofunctional (pale, or "cold"). The focal rounded defect lacking uptake (cold nodule) is characteristic of thyroid neoplasms and cysts. A focal rounded area of increased uptake that suppresses the remaining thyroid gland (hot nodule, not pictured) is most often a hyperfunctional follicular adenoma or goiter nodule.

This is a lobectomy specimen of thyroid gland showing normal parenchyma, within which is a 2-cm, white, slightly irregular, expansile tumor. No grossly discernible papillae are present on the cut surface. The neoplasm is not encapsulated, but is well demarcated from adjacent, beefy-red thyroid normal parenchyma, and it appears to distend and distort the capsule of the thyroid gland without penetrating through it.

Why would the lesion appear as a cold nodule on radioactive iodine scan? 
Carcinoma is less efficient than normal tissue in taking up iodine.

What would be the most likely sites of metastasis for this neoplasm? 
Regional lymph nodes in the neck are the most likely site of metastasis.

Exposure to which mutagenic agent is known to increase the incidence of this tumor? 
Exposure to radiation increases the incidence of this tumor.

Numerous papillary fronds, showing a delicate branching architecture with central fibrovascular cores, protrude into clear spaces.

Can papillary thyroid carcinomas form follicles? 
Yes, most do.

Can they lack papillary architecture? 
Yes, they can lack papillary architecture; hence, the nuclear features, shown later, are important for diagnosis. The follicular variant of papillary carcinoma forms follicles and lacks papillae, but has characteristic nuclei of papillary carcinoma and behaves like papillary carcinoma.

Papillae are present within a clear space representing a cystic cavity. The neoplastic papillae are lined by a single row of uniform, columnar epithelial cells, and have central, delicate, fibrovascular cores. Image 8 shows nuclear features. Papillary carcinomas may also show numerous calcospherites with concentric lamellae (psammoma bodies).  Near center.

What is the prognosis for patients with papillary thyroid carcinoma? 
Papillary thyroid carcinoma has about a 98% 10-year survival. The few patients who do poorly tend to be elderly, with invasion out of the thyroid gland into adjacent structures, and with distant visceral metastases. Cervical lymph node metastases do not significantly influence survival in patients with papillary thyroid carcinoma. Papillary carcinoma may also evolve into other, more aggressive subtypes of thyroid carcinoma (anaplastic carcinoma or poorly differentiated carcinoma) in a small proportion of patients.

Name other neoplasms that contain psammoma bodies. 
Other neoplasms that contain psammoma bodies include meningioma, ovarian papillary serous carcinoma, and, rarely, many other types. Psammoma bodies are thought to represent dystrophic calcification with a necrotic cell as a nidus, especially in papillary neoplasms.

The papillae shown here are covered by cuboidal epithelium that has nuclei that are characteristic of papillary thyroid carcinoma: large, crowded, and overlapping nuclei with vesicular chromatin, small nucleoli, infrequent mitotic figures and loss of polarity. Chromatin clearing (ground-glass "Orphan Annie" nuclei) and irregular nuclear contours with grooves and cytoplasmic pseudoinclusions are hallmark features of papillary thyroid carcinoma. Shared features between histopathology and cytology of papillary thyroid carcinoma are nuclear enlargement, intranuclear inclusions, nuclear grooves, small nucleoli, and nuclear overlapping. In contrast to tissue sections, cytologic smears of papillary thyroid carcinoma show finely granular chromatin (inset). Normal follicular cells are roughly the same size as a mature lymphocyte nucleus or a red blood cell. The inset shows nuclear detail, but the cytoplasm of the tumor cells is pale.

What is the significance of papillary carcinoma in this patient with Graves disease? 
There is no known association between papillary carcinoma and Graves disease. Both are common diseases, and their occurrence together is coincidental.

What genetic alteration may be found in papillary thyroid carcinoma? 
BRAF mutations are thought to be the most frequent recurrent genetic aberrations in papillary thyroid carcinoma occurring in approximately 40% of cases. RAF is a serine/threonine kinase downstream of RAS that transmits a mitogenic signal to the MAP kinase pathway. Mutations in the B isoform of RAF cause constitutive signaling through the MAP kinase pathway promoting tumorigenesis.

A 38-year-old attorney reported for her yearly physical examination complaining of tiredness, difficulty concentrating on her work, and a noticeable decline in her memory over the past several months. She attributed many of these symptoms to the severe stress generated by her legal caseload. Further questioning by her physician revealed that the frequency of her bowel movements had decreased from once daily, 6 months ago, to once every 2 or 3 days. She was having difficulty avoiding gaining weight, and despite warm weather, she felt chilled without a light sweater. Her only medication was an oral contraceptive.

Physical examination revealed a well-proportioned woman, 65 inches (1.65 m) tall, weighing 125 lb (56.7 kg). Physical examination also revealed sparse eyebrows (particularly at the lateral margins) and a diffusely moderately enlarged thyroid gland with a prominent pyramidal lobe above the isthmus.

Laboratory values were as follow:

Fine needle aspiration of the pyramidal lobe revealed lymphocytes, plasma cells, and cohesive clusters of enlarged follicular cells with nucleoli and abundant eosinophilic, granular cytoplasm (Hurthle cells). The patient was placed on medication and asked to come for follow-up.

Fleshy, soft, pale lobular nodules protrude from the cut surface, reflecting the marked lymphoid infiltrate in the gland. The depressed areas in between the pale nodules are due to fibrosis. Some cases show a greater degree of fibrosis than this example. Although the nodularity is uniform in this example, it may be quite asymmetric, manifesting as a palpable dominant nodule in some patients.

What appearance would you expect for the radioactive iodine scan in such a case? 
The distribution of iodine would be inhomogeneous because some parts of the gland are functional, and others are not; overall there would be decreased uptake.

Much of the thyroid parenchyma is replaced by a dense lymphocytic infiltrate that includes lymphoid follicles with germinal centers. Thyroid follicles are generally small, and they may undergo atrophy with metaplasia of the solid epithelial clusters to Hürthle cells (seen in the next image). Interstitial fibrosis also may be prominent in Hashimoto thyroiditis.

What other thyroid diseases show lymphocytic infiltrates? 
Graves disease, chronic thyroiditis, granulomatous thyroiditis, and Riedel thyroiditis also show lymphocytic infiltrates.

At higher power, the lymphocytic and plasma cell infiltrate with germinal center formation is easily appreciated. Hürthle cell metaplasia of atrophic thyroid follicles is represented by cells with increased cytoplasm showing eosinophilic granularity, and nuclear enlargement with some reactive atypia.

Patients with Hashimoto thyroiditis may have circulating antithyroid autoantibodies; what processes contribute to the formation of these antibodies? 
Two processes contribute to the formation of these antibodies. (1) Autoimmune disease process: lymphocytes make antibodies against TSH (thyroid-stimulating hormone, thyrotropin) receptors. The TSH receptor is a G protein-coupled transmembrane receptor whose action is inhibited in Hashimoto thyroiditis and stimulated in Graves disease. There is linkage to HLA-DR5 and HLA-DR3 in Hashimoto thyroiditis. (2) Destruction of follicles: results in exposure of antigens usually hidden, which may incite an immune response with formation of antithyroid peroxidase and antithyroglobulin antibodies.

What is the result of progression of Hashimoto thyroiditis to its end stage? 
Hypothyroidism with destruction of follicles and fibrous replacement of the gland.

In this case, how can one explain the total T₄ level within reference range in spite of hypothyroidism? 
TSH is the most sensitive and reliable test for thyroid function. It exquisitely measures the response of the pituitary gland to ambient thyroxine. Each person's free T₄ and total T₄ generally are maintained within narrow limits compared with the reference range for the entire population. For this reason, TSH is a far more sensitive test because TSH secretion responds in logarithmic fashion to small deviations of T₄. The total T₄ reflects the majority bound to proteins and the small amount of active free T₄. Birth control pills are one of many substances that can increase the quantity of binding proteins and drive up the level of total T₄ without changing the free fraction.

Initial symptoms are fatigue, lethargy, cold intolerance, and general listlessness and apathy with slowing of speech and intellectual function. Other findings of the generally slowed metabolism include constipation, decreased sweating, slow motor function, and dilation of cardiac chambers with poorly functioning myocytes (hypothyroid cardiomyopathy). With chronic myxedema, there is periorbital edema; tongue enlargement; and thickened, dry, coarse skin with thickening of facial features.

What are the causes and clinical features of congenital hypothyroidism? 
Causes include iodine deficiency during pregnancy, inborn errors of metabolism, and antithyroid therapy during pregnancy. Clinically, there is retardation of physical and mental growth. The changes usually do not manifest until weeks to months after birth, at which time changes are largely irreversible. For this reason, most states require that all infants be screened at birth for hypothyroidism.

The thyroid gland on the left is small and pale, representing atrophy and replacement of normal parenchyma by fibrous tissue, compared with the normal gland on the right. The gland on the left also could represent a thyroid gland after external irradiation to the neck or Graves disease treated with excessive radioactive iodine.

What is another potential long-term thyroid complication of irradiation to the neck? 
Papillary thyroid carcinoma is another potential long-term thyroid complication of irradiation to the neck.

A few atrophic residual follicles are present in a dense fibrous stroma containing scattered lymphocytes and plasma cells.

What treatment is indicated in end-stage Hashimoto thyroiditis and other forms of hypothyroidism? 
Thyroid hormone replacement is the treatment indicated.

A 50-year-old female Cambodian refugee presents with enlargement of a long-standing neck mass. Physical examination reveals a multinodular thyroid gland that moves with swallowing. There is a dominant, left-lobe, 6-cm nodule, which the patient said had enlarged abruptly 10 days before. Her thyroid gland extends below the sternal notch into the anterior mediastinum so that the inferior portion is not palpable.Fine-needle aspiration (FNA) of the dominant left-lobe mass shows evidence of a hemorrhagic colloid cyst.

The patient is taken to surgery because of her sensation of laryngeal compression, and a total thyroidectomy is performed. The pathologist notes a multinodular goiter and confirms the large hemorrhagic cyst, but also finds a solid 2.5-cm nodule in the mediastinal portion of the thyroid gland. The mass is thickly encapsulated, but enlarged follicular cells forming small follicles penetrate the capsule and invade vascular channels around the nodule.

The patient does not return for follow-up visits until 1 year later, when she notes pain in her left humerus. On x-ray studies, a lytic lesion is found, as are several small nodules in the lungs. Her TSH (thyroid-stimulating hormone, thyrotropin) level is markedly elevated.

The mass is relatively symmetric and diffusely enlarges the thyroid gland. The patient is from an endemic goiter area (in this case, Cambodia), where more than 10% of the population have goiters because of low-iodine diets (lack of seafood or iodized salt), often combined with diets high in vegetables that block iodine uptake by the thyroid gland (goitrogens, such as cabbage or cassava).

What symptoms might this mass cause? 
Difficulty in breathing or swallowing, especially after intrathyroidal hemorrhage.

Compare and contrast clinical features of goiter with those of thyroid neoplasms. 
Goiters generally have multiple nodules. Peak occurrence is during menstruating years of women, and patients are usually euthyroid. Thyroid neoplasms generally are solitary masses. They occur in patients over a wider age range than do goiters; patients are also usually euthyroid (although the nodule itself may be cold). Fixation to adjacent structures and hoarseness because of invasion of the recurrent laryngeal nerve are findings of advanced carcinoma.

What does the abrupt enlargement of the thyroid nodule indicate? 
Abrupt enlargement of a thyroid nodule usually indicates hemorrhage into a preexisting goiter nodule, although hemorrhage into a neoplasm can also occur spontaneously. Most thyroid neoplasms are slow-growing, but the uncommon anaplastic carcinoma grows visibly over weeks.

The thyroid gland shows multiple nodules on cut surfaces. Some nodules show cystic degeneration, hemorrhage, fibrosis, and calcification.

What is the biochemical stimulant to hyperplasia in goiter? 
Goiters usually form when some derangement that hampers thyroid hormone output causes compensatory elevation of the TSH level. TSH causes hyperplasia and hypertrophy of thyroid epithelium.

What is the usual functional outcome of goiter? 
Euthyroidism is the usual functional outcome of goiter.

Can the patient be hyperthyroid or hypothyroid? 
Yes, a patient with a goiter may be hypothyroid, hyperthyroid, or euthyroid. There is no way to determine the functional status of a goiter based on gross or microscopic examination

How would a radioactive iodine scan look in a thyroid gland such as the one pictured here? 
The scan would show heterogeneous uptake, and patchy warm and cold nodules.

A solitary, circumscribed, encapsulated, solid, homogeneous mass is shown in an otherwise normal thyroid lobe. Lobectomy is usually regarded as the minimal acceptable surgery for a dominant thyroid nodule, which may prove to be malignant. Follicular adenoma is distinguished from minimally invasive follicular carcinoma only by capsular or vascular invasion in the latter, which generally cannot be appreciated grossly

What clonal genetic abnormalities have been identified in thyroid follicular adenomas? 
Somatic mutations that affect the TSH receptor or its coupled G protein component, G_sα, are found in many functional follicular adenomas. Uncoupling of TSH from cyclic adenosine monophosphate (cAMP) production causes the cells to be chemically stimulated to proliferate by excess cAMP, producing an autonomous neoplastic nodule. There is no current evidence that follicular carcinomas arise from preexisting follicular adenomas.

At low power, there is a delicate but complete fibrous pseudocapsule (formed by compression of adjacent tissue) separating the adenoma from adjacent thyroid tissue.

What histologic features would you look for to rule out follicular carcinoma? 
Follicular carcinomas may be very well differentiated; the presence of vascular or capsular invasion is essential to make the diagnosis of carcinoma

Review expected results of radioactive iodine scans in follicular adenoma and follicular carcinoma, including metastases after total thyroidectomy. 
Follicular adenomas are usually cold, but may also be hot or warm. Follicular carcinoma generally is cold when scanned with an intact thyroid gland, but metastases may show uptake after total thyroidectomy.

What is the prognosis for patients with follicular carcinoma? 
The prognosis depends on the amount of capsular and vascular invasion present. Minimally invasive tumors have an excellent prognosis with an overall disease-free survival rate of 95%. In contrast, 50% of patients with widely invasive follicular carcinomas eventually die of their malignancy.

This neoplastic tissue is very well differentiated, showing follicles containing colloid. The nuclei are uniform and round with some small nucleoli and no mitotic figures, and polarity of the cuboidal cells toward follicular lumens is preserved.

How do the follicular cells in an adenoma compare with normal thyroid parenchyma?
Follicular cells in adenomas tend to have larger nuclei and a slightly higher N:C ratio than non-neoplastic thyroid tissue, but are often indistinguishable from non-neoplastic thyroid epithelial cells.

A 35-year-old obese woman presented to her physician with weakness, mainly of the shoulders and thighs. She also complained of increasing thirst, headache, and easy bruising. Further inquiry revealed that her menses were getting more scanty, and that she felt depressed. On physical examination, she was found to have a puffy face (moon facies) and truncal obesity. She also had purple striae on the lateral aspects of her abdomen. Her blood pressure was 180/110 mm Hg. Strength in the proximal muscles of her shoulders and hips was reduced.

Because of this constellation of symptoms and signs, an endocrine disorder was suspected as a possible explanation for her presentation. Laboratory investigations revealed a plasma glucose of 300 mg/dL (normal 70-110 mg/dL). An overnight dexamethasone suppression test was ordered, and this revealed that the plasma cortisol the next morning was 10 μg/dL (normal <5 μg/dL). The patient was admitted to the hospital and underwent further testing. Her plasma cortisol at 9:00 A.M. was 28 μg/dL (normal 10-25 μg/dL) and at 6:00 P.M. was 25 μg/dL (normal <10 μg/dL). The patient's 24-hour urine free cortisol was 200 μg/day (normal <50 μg/day). Her plasma ACTH was 125 pg/mL (normal 20-100 pg/mL). A low-dose dexamethasone suppression test (0.5 mg/6 hr for 48 hours, 2 mg/day) with urine collected for 17-hydroxycorticosteroids (17-OHCS) showed urinary 17-OHCS were 12 mg/day (normal <4 mg/day). The patient underwent a high-dose dexamethasone suppression test (2 mg/6 hr for 48 hours, 8 mg/day), and this revealed that urinary 17-OHCS were suppressed by 70% to 3.6 mg/day after high-dose dexamethasone. Thereafter, the patient underwent imaging studies of the brain and adrenal glands.

Classic physical findings in Cushing syndrome include moon facies, truncal obesity, buffalo hump, striae, hirsutism, easy bruising, hypertension, proximal muscle weakness, menstrual abnormalities, and glucose intolerance or diabetes mellitus.

Which biochemical tests support the diagnosis of Cushing syndrome in this case? 

The following biochemical abnormalities support the diagnosis of Cushing syndrome:

1. Increased urine free cortisol.

2. The lack of diurnal rhythm of serum cortisol; normally cortisol is significantly higher in the morning than in the evening.

3. Failure to suppress cortisol in the plasma and urine overnight and low-dose dexamethasone suppression tests.

Usually the simplest outpatient screening test to exclude a diagnosis of Cushing syndrome is the overnight plasma dexamethasone suppression test, in which 1 mg of dexamethasone is administered at 11:00 P.M., and a plasma cortisol is drawn at 8:00 A.M. the next morning. If the plasma cortisol is less than 5 μg/dL, this rules out the diagnosis of Cushing syndrome. If the plasma cortisol is greater than 10 μg/dL, this is consistent with the diagnosis of Cushing syndrome and requires further investigation, such as assay of 24-hour urine free cortisol and low-dose and high-dose dexamethasone suppression tests.

What is the biochemical basis of these changes? 
The clinical features of Cushing syndrome are primarily due to excessive cortisol, which is the major glucocorticoid, but can also result from some mineralocorticoid activity. Sodium and water retention leading to hypertension and potassium wasting causing hypokalemic alkalosis are common findings. Many patients with Cushing syndrome have impaired glucose tolerance or diabetes mellitus because of the anti-insulin effects of cortisol, which stimulates hepatic gluconeogenesis and decreases peripheral glucose uptake. The proteolytic effect of cortisol can result in osteoporosis, muscle wasting with weakness (myopathy), and thinning of the skin with increased bruising and purple striae. The increase of adrenal androgens, such as DHEA and androstenedione, and their peripheral conversion to testosterone account for the common findings of androgen excess, including acne, hirsutism, and menstrual disturbance. Psychiatric disturbance, particularly depression, may be a prominent feature of hypercortisolism.

Both adrenal glands are shown, exhibiting nearly confluent nodularity of the cortex. The tests that are most useful in delineating the site of the lesion in Cushing syndrome are plasma ACTH level and high-dose dexamethasone suppression test.

Could a patient who had adrenal glands like this have Cushing syndrome? 
Yes; a pituitary corticotroph adenoma, an ectopic ACTH-producing tumor, or exogenous excess ACTH would produce similar hyperplasia of the adrenal cortex and Cushing syndrome.

Could a patient who had adrenal glands such as this have hyperaldosteronism? 
Yes, although it is uncommon. In 80% of cases, hyperaldosteronism results from a functional adenoma. In the others, spontaneous adrenocortical hyperplasia is responsible

Could a patient who had adrenal glands such as this have adrenogenital syndrome? 
Yes; lack of cortisol production (because of a congenital enzyme deficiency, most often 21-hydroxylase deficiency) causes marked ACTH release by corticotrophs and consequent adrenal nodular hyperplasia.

Could this patient have a lesion in the pituitary gland? 
Yes, the patient could have a corticotroph adenoma in the pituitary gland.

The adrenal cortex shows several nodules of roughly equal size, incompletely separated by connective tissue septa. The medulla is not involved; it is a basophilic central zone around the central vein (not pictured here). The cortical nodules are pale due to abundant cytoplasmic lipid content.

What accounts for the high lipid content of the adrenal cortex? 
The cells store and utilize cholesterol as the substrate for producing steroid hormones.

At high power, the proliferating cells resemble normal zona fasciculata, showing fairly uniform nuclei centrally and cytoplasm distended by lipid droplets.

What is the major cytoplasmic organelle involved in steroid hormone production? 
Smooth endoplasmic reticulum is the major cytoplasmic organelle involved in steroid hormone production.

The yellow-brown strip of adrenal cortex is thinned to 1-2 mm, and the gland weight is less than 5 gm.

What cells are present in the adrenal cortex, and what do they secrete? 
Glomerulosa layer secretes aldosterone. Fasciculata and reticularis layers secrete cortisol and sex steroids.

Could this patient have had Cushing syndrome? 
Yes. Exogenous corticosteroid therapy, resulting in pituitary corticotroph suppression and adrenocortical atrophy, could produce Cushing syndrome.

Could this patient have had Addison disease? 
Yes; with such severe atrophy of the adrenal cortex, the patient would have Addison disease (if exogenous corticosteroids were not administered).

What are the common causes of hypoadrenalism? 
Autoimmune lymphocytic adrenalitis, granulomatous infections of the adrenal glands, and anterior pituitary failure are common causes of hypoadrenalism. Metastases to the adrenal glands usually do not affect adrenal function.

In this case, the solitary yellowish nodule is circumscribed; the adjacent residual nonneoplastic adrenal cortex is thinned and atrophic.

Why is this not an example of an adenoma producing pure hyperaldosteronism? 
In the example shown, the glucocorticoid-producing adenoma has reduced ACTH production because of feedback inhibition of the pituitary corticotrophs, causing atrophy of the normal adrenal cortex. An adenoma that produced only aldosterone would not affect the secretion of ACTH.

How does one differentiate an adenoma from a carcinoma of the adrenal cortex? 
Metastases, large size, necrosis, mitotic figures, and vascular invasion characterize carcinoma of the adrenal cortex.

The neoplasm is well circumscribed and is dominated by pale, lipid-laden cells.

This high-power photomicrograph shows clear lipid-containing cells in nests. Note the delicate vascular network between the nests.

Is it possible to distinguish the appearance of these cells from normal cells of the adrenal cortex or a nodule of hyperplasia? 
Not microscopically. By molecular analysis, cells in an adenoma would be clonal

This large yellow and red mass has been resected. The cut surface shows irregular coloration of the mass, reflecting patchy necrosis.

Why are adrenal cortical carcinomas generally much larger than adenomas when they come to clinical attention? 
Carcinoma cells are less efficient at producing hormones than are adenoma cells, which are less efficient than normal cells. The carcinoma must become large to produce enough hormones to yield an endocrine syndrome or to produce symptoms by mass effects.

A 32-year-old man experienced several episodes of headaches, dizziness, and loss of consciousness in the mornings. During one of these episodes, his blood glucose was 40 mg/dL, suggesting fasting hypoglycemia. After a 24-hour fast, he became hypoglycemic (38 mg/dL) with serum insulin 35 μU/mL (normal <20 μU/mL) and insulin C peptide 5 ng/mL (reference range 0.5-2 ng/mL). The insulin-to-glucose ratio was 0.92 (normal <0.3).

A CT scan of his abdomen and an arteriogram revealed a highly vascularized small tumor in the body of the pancreas, which was excised. The tumor measured 2 cm, was well demarcated, and had a yellow-tan cut surface. A gallstone was palpable in the gallbladder at laparotomy, apparently asymptomatic, but a prophylactic cholecystectomy was performed.

The patient remained symptom-free after surgery. A screening chemistry test showed his serum calcium to be slightly elevated, however, at 11.5 mg/dL. A radionuclide bone scan showed no evidence of metastases. When rechecked, his serum calcium was the same, his serum inorganic phosphorus was slightly low, his serum total protein was normal, and his serum intact parathyroid hormone (PTH) was 60 pg/mL (reference range 10-65 pg/mL).

MEN I

This cross section of pancreas shows a circumscribed, firm, pale mass that is homogeneous except for a central yellow focus of necrosis.

How does one determine which hormones are made by the tumor? 
Serum testing and assessment of the patient's symptoms determine which hormones are made by the tumor.

Why is the history of hypoglycemia and hyperinsulinemia important? 
Although there are many causes of hypoglycemia, only insulinomas are characterized by hypoglycemia, hyperinsulinemia, and elevated levels of plasma insulin C peptide. The self-induction of hypoglycemia by injection of insulin or ingestion of sulfonylureas, so-called factitious hypoglycemia, is not accompanied by high serum levels of insulin C peptide.

Note the resemblance of these uniform tumor cells to the cells in normal islets of Langerhans. The cells form cords, ribbons, and solid nests with a delicate vascular plexus.

How do islet cells package and release their hormone product? 
The hormones are packaged in dense-core neurosecretory granules that enter the blood by exocytosis.

What is the Whipple triad? 
1) Symptoms of hypoglycemia are present, especially confusion, stupor, or loss of consciousness. 2) Hypoglycemia is present, typically glucose less than 50 mg/dL. 3) Attacks are precipitated by fasting or exercise and are promptly relieved by administration of glucose.

Patients with primary hyperparathyroidism have elevated PTH levels, which cause hypercalcemia. Patients with hypercalcemia secondary to malignancy with destructive bone metastases have appropriately suppressed PTH levels. Patients with hypoparathyroidism have low PTH and hypocalcemia. Patients with secondary hyperparathyroidism generally have serum calcium levels slightly below the normal range, but with markedly elevated PTH levels (not pictured).

The normal parathyroid glands (usually four) are tan and are most often found in the groove between the lateral thyroid lobes and the trachea. Ectopic locations are common.

Review the embryologic formation and migration of thyroid and parathyroid glands. 
Thyroid follicular cells migrate from the midline tongue base down the anterior neck. Upper parathyroid glands migrate from the fourth pharyngeal pouches with C cells (from the neural crest) to the upper lateral thyroid lobes. Lower parathyroid glands migrate from the third pharyngeal pouches with thymic anlage to the lower thyroid pole regions. Ectopic locations of parathyroid glands are common.

This parathyroid adenoma shows a fibrous capsule demarcating it from residual non-neoplastic parathyroid (not pictured). Parathyroid adenomas typically contain no adipocytes, which are abundant in normal parathyroid tissue. Pleomorphic nuclei may be present, and mixed cell types may include chief cells, oxyphil cells, and transitional forms.

Compare and contrast parathyroid adenoma with primary parathyroid hyperplasia and with parathyroid carcinoma. 
All three produce excess PTH and manifest with hypercalcemia.

Adenoma—one gland enlarged, cytologically bland (although may have some polyploid large nuclei), may have rim of suppressed normal tissue; other glands suppressed.

Primary hyperplasia—usually affects all parathyroid glands (although often asymmetrically), lacks atypia, often familial or part of MEN syndrome. (MOST COMMON)

Carcinoma—similar to adenoma, but usually larger (several grams), often with mitoses, fibrous bands, and invasion of adjacent structures and blood vessels.

At high power, the chief cells form solid organoid nests, sheets, and small follicles with a delicate capillary plexus. This example shows fairly uniform nuclei.

What genetic defects have been identified in parathyroid adenomas? 
Tumor-specific (not germline) mutations have been identified as parathyroid adenoma I (PRAD1) and MEN1. PRAD1 encodes cyclin D1, a cell cycle regulator on chromosome #11; PRAD1 can undergo inversion so that it is next to the 5′-PTH gene regulatory sequences. A regulatory element of the 5?-PTH gene directs overexpression of cyclin D1, causing clonal proliferation (adenoma or hyperplasia). Tumors in patients with MEN I syndrome and some sporadic cases of parathyroid adenoma have homozygous loss of the putative suppressor gene MEN1 on chromosome band 11q13. The MEN1 gene product shows no significant homology to known proteins, and its cellular functions are unknown.

The hyperplastic gland is very cellular with organoid parathyroid tissue and scant residual entrapped adipocytes. This patient had adult-type polycystic kidney disease with renal failure and enlargement of all four parathyroid glands.

Compare and contrast primary and secondary parathyroid hyperplasia. 

Primary and secondary parathyroid hyperplasia are histologically similar, but clinically quite different.

Primary—autonomous high PTH causes hypercalcemia; treated surgically (excise 3½ glands).

Secondary—hypocalcemia (most often secondary to renal failure) stimulates parathyroid hyperplasia; treated by calcium supplementation (or renal transplantation).

What is the most likely diagnosis in this case? 
This patient has a tumor of the pancreatic islet cells and evidence of hyperparathyroidism. Together these suggest a diagnosis of MEN I. The patient should be investigated for a pituitary adenoma that may be small and nonfunctional.

This image shows a mix of chief cells (pale with granular cytoplasm), water-clear cells (clear cytoplasm), and nonfunctional oxyphil cells (eosinophilic with granular cytoplasm).

By what mechanism does renal failure cause hypocalcemia? 
Decreased phosphate excretion causes elevated serum phosphate, which directly depresses the serum calcium level.

What are some less common causes of secondary hyperparathyroidism? 
Less common causes of secondary hyperparathyroidism include inadequate dietary calcium intake, vitamin D deficiency, and steatorrhea.

A 22-year-old man presents with hypertension, episodic headaches, sweating, and palpitations for several months. He has also noted a painless left neck nodule for 2 months. He reports that his father died suddenly at age 35 of an apparent heart attack. His two younger siblings are healthy.

Physical examination reveals blood pressure 150/90 mm Hg and pulse 80 beats/min and regular. A 3-cm enlarged lymph node is palpable adjacent to the lateral border of, but separate from, the left thyroid lobe without other obvious cervical or thyroid lesions. Cardiac and abdominal examinations are normal. The patient notes onset of a headache and palpitations while waiting for an electrocardiogram to be performed. During this episode, his blood pressure is noted to be 180/110 mm Hg.

Laboratory tests show normal serum calcium, glucose, and thyroid function tests. Urinary metanephrines (catecholamine breakdown products) are elevated to 5.2 mg/dL (normal <1.3 mg/dL). CT scan of his abdomen shows a 4-cm nodule in the left adrenal gland and a normal right adrenal gland.

Fine-needle aspiration of the left neck mass shows fragments of amyloid and atypical epithelial cells without evidence of colloid or follicular differentiation. An immunohistochemical stain for calcitonin is positive.

This solid pink-gray mass appears well circumscribed. Note the rim of residual adrenal cortex around the mass, and the remaining uninvolved portion of the adrenal gland at the right.

Contrast this gross appearance with an adrenalcortical adenoma and carcinoma. 
Adrenocortical tumors are usually yellow, or occasionally brown; tumors causing Cushing syndrome may cause atrophy of uninvolved adrenal cortex. Adenomas are usually less than 50 gm, and carcinomas are usually greater than 50 gm. Pheochromocytomas are generally pink-to-gray, spare the cortex, and have an average size of 100 gm (although this is quite variable).

What is the likelihood of a pheochromocytoma being malignant? 
The likelihood of a pheochromocytoma being malignant is 10%.

What syndrome does this patient have? 
This patient most likely has multiple endocrine neoplasia (MEN) type IIA. There is evidence of pheochromocytoma and a medullary carcinoma of the thyroid (with metastasis to a cervical node). Parathyroid hyperplasia may also occur in MEN IIA, but in this patient, who has normal serum calcium, that is unlikely. Also, there is no marfanoid body habitus or mucosal neuromas, which are hallmark features of MEN IIB.

This pheochromocytoma has compressed the adrenal cortex and capsule to a thin rim (not pictured). The tumor is arranged into organoid (solid) nests separated by a delicate capillary plexus. Some necrotic foci may be present.

What criterion establishes a pheochromocytoma as malignant? 
The prediction of malignancy in a pheochromocytoma is difficult and relies on the assessment of multiple histologic features. Ultimately, the only single parameter that definitively dictates malignancy is the presence of metastases.

The adrenal medullary cells of pheochromocytoma may have ill-defined (syncytial) cytoplasmic margins, and the nuclei can be uniform or quite variable. A moderate amount of granular cytoplasm is typical; it contains neurosecretory granules comprising epinephrine and norepinephrine

What are the clinical effects of these hormones? 
Clinical effects include increased heart rate, vascular tone, and blood pressure, and decreased blood flow to the gut and kidneys. Excessive levels of these hormones may also precipitate congestive heart failure, pulmonary edema, angina pectoris, myocardial infarct, arrhythmia, cerebral hemorrhage, and death.

What laboratory tests are used to diagnose pheochromocytoma? 
Urinary metabolites of catecholamines (metanephrines and normetanephrines) are used to diagnose pheochromocytoma.

What are the clinical features and complications of pheochromocytoma? 
The clinical features and complications of pheochromocytoma include hypertension that may be episodic, sustained, or sustained with paroxysms; palpitations; headache; heart failure; and strokes

Numerous membrane-bound, dense-core neurosecretory granules are present, in which catecholamines are stored. The granules are slightly smaller than adjacent mitochondria and are present near the cytoplasmic membrane (30,000X magnification).

Name other endocrine neoplasms that have these structures. 
Pituitary adenomas, medullary thyroid carcinomas, parathyroid adenomas and carcinomas, pancreatic endocrine (islet cell) tumors, and carcinoid tumors also contain neurosecretory granules.

A solid, firm, white mass has replaced nearly the entire thyroid lobe. Regional lymph nodes looked similar.

What are the cells that give rise to medullary carcinoma of the thyroid? 
C cells give rise to medullary carcinoma of the thyroid.

Why do medullary carcinomas not arise within the thyroid isthmus or thyroglossal duct remnants? 
C cells migrate separately from follicular cells embryologically. C cells migrate from the neural crest to the lateral thyroid lobes; follicular cells migrate from the midline tongue base down the anterior neck.

Cords and nests of relatively uniform neoplastic cells are present in a matrix of amyloid.

Do these tumor cells secrete a hormone? 
Yes. Calcitonin is most common; occasionally others, such as ACTH, are secreted.

What are the biochemical effects of the hormone? 
Calcitonin may help to reduce serum calcium, but not at physiologic doses in humans. It may contribute to diarrhea when markedly elevated.

Does this tumor occur in a familial form? 
Yes, this tumor occurs as a component of MEN IIA and MEN IIB (also known as MEN III, mucosal neuroma syndrome) and isolated familial medullary thyroid carcinoma.

What genetic alteration is characteristic in familial forms of medullary thyroid carcinoma? 
The RET proto-oncogene, which encodes a tyrosine kinase receptor, shows germline point mutations. These affect residues in the cysteine-rich extracellular domains or in the intracellular tyrosine kinase domains constitutively to activate the receptor, resulting in gain of function. Because the RET gene is normally expressed in thyroid C cells, constitutive activation causes the cells to undergo neoplastic transformation (a dominant oncogene). In the MEN IIB mutation, a single amino acid change affects a critical region of the tyrosine kinase catalytic core, and is responsible for development of mucosal neuromas.

In what other thyroid cancer is alteration of the RET gene found? How is the alteration different? 
The RET gene is often overexpressed in papillary thyroid carcinoma, but the gene does not show germline mutations in papillary carcinoma as it does in familial forms of medullary thyroid carcinoma. Review Endocrine Case 2, Image 8, second question.

How does the biologic behavior of medullary carcinoma compare with that of papillary and follicular thyroid carcinomas? 

Papillary carcinoma—frequent lymph node metastases, infrequent visceral metastases, fatality rare (<5%). (THINK NUCLEAR ATYPIA)

Follicular carcinoma—rare lymph node metastases, moderate rate of visceral metastases, moderate fatality (about 20%). (CONTRAST FOLLICULAR ADENOMA)

Medullary carcinoma—common lymph node and visceral metastases, fatality common (about 50%).

What is the origin of the amyloid? 
Excess procalcitonin deposition.