Hyperkeratosis and hypergranulosis

Parakeratosis: corneal layer with retained keratinocyte nuclei

Acanthosis: epidermal hyperplasia

*notice that the ridges all go to pretty much the same depth

Papillomatosis: projection of dermal papilla above the surface of the skin

*common with warts

Dyskeratosis: premature keratinization and death of a keratinocyte

Acantholysis: loss of/damaged desmosomes→loss of cohesion of keratinocytes in the epidermis, cells "round up"

Spongiosis: epidermal intercellular edema

*think eczematous dermatitis!

Vitiligo: decreased/absent melanocytes and melanin pigment

Junctional nevus: pigmented macule of the epidermis

Junctional nevus: nested aggregates of melanocytes within the ridges of the epidermis

Intradermal nevus: flesh-colored papule of the dermis

Intradermal nevus: melanocyte proliferation in the dermis

Compound nevus: pigmented papule

Compound nevus: nested aggregates of melanocytes within the ridges of the epidermis + melanocyte proliferation in the dermis

Dysplastic nevus: nevus with ABCDE qualities of melanoma grossly and on histology

Dysplastic nevus

• Architectural changes
• Cytologic atypia
• Stromal response

Dysplastic nevus

• Architectural changes
• Cytologic atypia
• Stromal response

Melanoma: malignant proliferation of melanocytes

• Asymmetrical
• Border irregularity
• Color variation
• Diameter >6mm

Melanoma

Seborrheic keratosis: brown plaques, well-circumscribed

• Look "stuck on"
• Can resemble melanoma

Seborrheic keratosis: well-demarcated proliferation of keratinocytes

• Often hyperkeratosis

Seborrheic keratosis: well-demarcated proliferation of keratinocytes

• Often hyperkeratosis

Acrochordon (skin tag): flesh-colored papule, pedunculated

• Eyelids, neck, axillae, groin

Acrochordon: epidermis covering a fibrovascular core

• No adnexal structures present

Acrochordon: epidermis covering a fibrovascular core

• No adnexal structures present

Epidermal inclusion cyst: nodule with black punctum

Epidermal inclusion cyst: demal cyst lined by epidermis and filled with keratinous material

Epidermal inclusion cyst: demal cyst lined by epidermis and filled with keratinous material

BCC: pearly papule with telangiectasia

BCC: ulceration with pearly rolled border

BCC: aggregates of pallisading basaloid cells

BCC: aggregates of pallisading basaloid cells

BCC superficial

BCC nodular

BCC micronodular

BCC infiltrative

Dermatofibroma: papule/nodule, firm

• Legs
• May be confused with a nevus

Dermatofibroma

• Epidermal hyperplasia
• Basal layer pigmentation
• Spindle-cell proliferation in the dermis
• Poorly circumscribed

Dermatofibroma

• Epidermal hyperplasia
• Basal layer pigmentation
• Spindle-cell proliferation in the dermis
• Poorly circumscribed

Pyogenic granuloma: solitary bleeding papule

• Fingers, gingiva

Pyogenic granuloma: ulcerated epidermis, proliferation of blood vessels in lobules

*no granulomatous inflammation!

Pyogenic granuloma: ulcerated epidermis, proliferation of blood vessels in lobules

*no granulomatous inflammation!

Angiosarcoma: ill-defined dark plaque, malignant neoplasm of endothelial cells

• Scalp (head/neck)
• Areas of previous radiation
• Lymphedema

Angiosarcoma:markedly atypical cells

• Interanastomosing vascular channels
• Solid sheets of cells

Urticaria: wheals (itchy plaques)

Urticaria: reticular derma edema, sparse infiltrate of neutrophils and eosinophils

Eczematous dermatitis: red papulovesicles with crust and scale

• Can develop into thick plaques with scales

Eczematous dermatitis: spongiosis

• Over time spongiosis becomes less prominent
• Replaced by epidermal hyperplasia and hyperkeratosis (corresponds to the thick plaques with scales on gross examination)

Erythema multiforme: papuloplaque/vesciles with targetoid configuration

• Acral skin (palms, soles)

Erythema multiforme: lymphocytic infiltrate in DEJ + necrotic keratinocytes (interface dermatitis)

Psoriasis: papulosquamous plaques with silver-white scale, well-demarcated

• Knees, elbows, scalp, lumbosacrum
• Perhaps nail pitting

Psoriasis

• Uniform epidermal hyperplasia
• Thickened cornified layer with parakeratosis and neutrophils (corresponds with the scale seen on gross examination)

DLE: thick plaques with scales, well-demarcated

• Sun-exposed skin

DLE

• Hyperkeratosis, plugged follicular infundibula
• Atrophy of epidermis
• Lymphocytic infilration in superficial and deep dermis
• Mucin deposition in the dermis

DLE: "positive lupus band," granular full house staining (IgG, IgM, C3) along DEJ

Pemphigus: Vesicles in skin and mucous membranes

Pemphigus: Vesicles in skin and mucous membranes

Pemphigus: supravasal vesicles

Pemphigus: fishnet staining (IgG) between/around keratinocytes

Bullous pemphigoid: tense bullae

Bullous pemphigoid: supepidermal bullae, dermal infiltrate of eosinophils

Dermatitis herpetiformis: pruritic papules/vesicles/bullae

• Symmetrically distributed on elbows, knees, butt

Dermatitis herpetiformis: neutrophilic microabscesses at the tips of the dermal papillae

Dermatitis herpetiformis: granular staining (IgA) at the tips of the dermal papillae

Verruca

Verruca

• Papillomatosis
• Hyperkeratosis
• Epidermal hyperplasia
• Coarse keratohyaline granules

Molluscum: flesh-colored papules with umbilication

• Usually multiple lesions

Molluscum: aggregates of viral particles

Molluscum: aggregates of viral particles

Dermatophytosis (ringworm): erythematous annular plaques with scales

Dermatophytosis (ringworm): parakeratosis (correlates with scale seen on gross examination)

Dermatophytosis (ringworm): PAS shows hyphae in cornified layer

Scabies: pruritic papules/vesicles/pustules, burrows

• Axillae, finger webs, groin, genitals

Scabies: mite/egg/feces in subcorneum, dermal infiltrate of lymphocytes and eosinophils

Autoimmune destruction of melanocytes

Proliferation of melanocytes in nests

• Epidermal: junctional
• Dermal: intradermal
• Both epidermis and dermis: compound

Increased risk of developing melanoma (↑# of nevi or family hx of melanoma)

Biopsy the more atypical ones

Complete excision and follow-up

UV light

In areas of chronic sun exposure and areas that are intermittently exposed to intense sun

Breslow thickness (depth of invasion) is the most important prognostic indicator

• <1mm thick have the lowest chance of mets
• >4mm thick have highest chance of mets

Also depends on ulceration, regional/distant mets

Common

Middle-aged+

Common

Common

Epidemiology

• Common
• Elderly
• Possible precursors to SCC

Sun exposure = found on sun-exposed areas

Hyperkeratosis, parakeratosis, keratinocytic dysplasia

2nd most common skin cancer

Sun-exposed skin, areas of previous radiation/chronic ulcers/burns/HPV

Proliferation of atypical keratinocytes, invasion into dermis

• Can be well-differentiated: resemble normal squamous cells
• Can be poorly-differentiated: vague squamous features, large pleomorphic nuclei, scant cytoplasm

Usually diagnosed early so mets are uncommon

Most common cancer

Usually sporadic, but congenital PTCH mutation predisposes to multiple BCCs at young age

Sun-exposed areas

Grow slowly, rarely met

• Untreated tumors may ulcerate and invade adjacent structures

Common, benign

Young adults

Young patients following trauma

Pregos

Uncommon

Immunohistochemical stains like CD31

IgE type1 hypersensitivity reaction: dermal mast cell degranulation→increased vascular permability→edema

Severe cases may have laryngeal edema→airway obstruction

Allergic or irritant contact dermatitis

Kids, young adults

Part of spectrum of SJS (mucous membranes) and TEN (sloughing of full-thickness necrotic epidermis)

Common, chronic

Familial?

Some patients will have psoriatic arthritis

AutoAb to demosomes (desmoglein 3--PV, desmoglein 1--PF)

Damaged desmosomes→acantholysis

Older folks

AutoAb against DEJ "bullous pemphigoid Ag 1 and 2"

Associated with celiac disease

IgA against gluten cross-reacts with papillary dermis or immune complexes are depositied in the papillary dermis

Kids, adolescents

Poxvirus via direct contact

Microsporum

Epidermophyton

Trichophyton

Sarcoptes scabiei