- Benign but locally invasive and aggressive odontogenic neoplasm apparently arising from ameloblasts

- Most common clinically significant odontogenic tumor; frequency equals the combined frequency of all other tumors excluding odontomas

- Can arise from epithelium of: dental lamina rests, devleoping enamel organ, lining of odontogenic cysts, or basal cells of oral mucosa

Conventional solid or multicystic intraosseous - 86%

Unicystic (intraosseous) - 13%

Peripheral (extraosseous) - 1%

- Age: most common in 3rd-7th decades of life but can occur at almost any age

- gender =

- Rade: none

- Location 80-85% in mandible, most commonly molar/ascending ramus area; in maxilla, posterior

- most often asymptomatic sweling or expansion of jaw; pain and paresthesia uncommon

- Most commonly a multilocular radiolucency, often accompanied by buccal & lingual cortical expansion

- Root resorption common; often assoc with unerupted molar (e.g. 3rd molar)

- May present as unilocular radiolucency resembling a cyst

(Exception: desmoplastic ameloblastoma commonly presents in anterior maxilla as a fibroosseous-like mixed radiolucency/opacity)

- All forms of conventional ameloblastoma have tendency to form cysts of various sizes from solely microscopic to grossly evident at surgery; within the background are 6 well-recognized patterns - in large lesions may be more than one

- Follicular, plexiform, acanthomatous, granular cell, desmoplastic and basal cell

- Most common and recognizable; islands of epithelium resembling enamel organ sitting in a background of mature CT:

- Epithelial nests: core of loosely arranged angular cells resembling stellate reticulum surrounded by a single layer of tall columnar cells resembling ameloblasts

- The ameloblast-like cells contain nuclei exhibiting reverse polarization (away from basement membrane), palisading with adjacent nuclei and often hyperchromatism

- Often show cyst formation ranging from microcysts to large cysts several cms in diameter

Particularly common in maxilla, long, anastomosing cords or sheets of odontogenic epithelium, each bounded by columnar or cuboidal ameloblast-like cells

- Supporting CT tends to be loosely arranged and vascular, cyst formation relatively uncommon

Similar to follicular pattern with addition of extensive squamous metaplasia in central (stellate reticulum-like) areas of islands

- Histologically could be confused with epidermoid carcinoma

Small islands and cords of odontogenic epithelium in a densely collagenized stroma

- Evidence of increased production of TGF-beta may cause desmoplasia; ameloblastoma-like cells may be inconspicuous

Surgical resection with a block of surrounding bone if possible without endangering neighboring vital structures (orbital contents, etc.)

- Curettage is usually inadequate setting the stage for recurrence

- Radiation inappropriate and risks subsequent osteosarcoma

Ameloblastoma apparently arising in association with the lining of a single odontogenic cyst

- Arises from either the lining of a pre-existing nonneoplastic odontogenic cyst (e.g. dentigerous cyst) or begins as a cystic neoplasm de novo (from the beginning), or both.

- Age: most common in younger pts, 50% during 2nd decade

- Site: 90% in mandible, mostly posterior

- S&S: mostly asymptomatic, but large lesions can cause painless swelling

- Most common clinical/radiographic presentation mimics dentigerous cyst, most often assoc with impacted 3rd molar; less commonly mimics other common odont cysts - lateral periodontal, apical periodontal, primordial, etc.

- Luminal unicystic ameloblastoma: tumor confined to luminal surface of cyst; fibrous wall with lining composed totally or partly of ameloblastic epithelilum: basal layer of columnar or cuboid cells with hyperchromatic nuclei showing reverse polarization and basal cytoplasmic vacuolization

- Intraluminal unicystic ameloblastoma: nodule(s) of ameloblastoma project from the cystic lining into the lumen of the cyst; may develop plexiform pattern within the IUA: plexiform unicystic ameloblastoma

- Mural unicystic ameloblastoma: fibrous wall infiltrated by typical folliculr or plexiform ameloblastoma

Controversial - in those cases in which both the surgical and histpathologic findings indicate complete excision has been achieved, especially if the ameloblastoma is confined to the lining, patients often managed by just careful followup

- If there is doubt completeness of surgical excision or if there is significant mural invasion of ameloblastoma, wider surgical re-excision is most prudent course

- Age: wide range but most in middle-aged adults, average 52 years

- Site: most commonly posterior gingival and alveolar mucosa, Mand>maxilla

- Usually painless, nonucleated sessile or pedunculated gingival or alveolar mucosal lesion, may resemble fibroma or pyogenic granuloma; most cases < 1.5 cm

Conservative surgical excision

Very good, small recurrence rate; malignant change has been reported but rare