Two unerupted teeth with pericoronal radiolucencies

Correct answer: D. Adenomatoid odontogenic tumour

• A. This is the commonest MISdiagnosis for the lesion described, and separating the two is the entire point of the item. A dentigerous cyst attaches AT the cementoenamel junction and surrounds the CROWN ONLY. It does not extend apically along the root, and it does not contain calcified flecks.
• B. The calcifying odontogenic cyst is characterised histologically by GHOST CELLS, often shows more substantial calcification, and is frequently associated with an odontoma. It is a reasonable differential but the described features fit AOT.
• C. Ameloblastic fibroma is a mixed odontogenic tumour of young patients, but it is expansile and favours the POSTERIOR MANDIBLE.
• D. CORRECT. The ADENOMATOID ODONTOGENIC TUMOUR is remembered as the ‘two-thirds tumour’: two-thirds occur in FEMALES, two-thirds in the ANTERIOR MAXILLA, two-thirds are associated with an UNERUPTED TOOTH — most often the canine — and two-thirds occur in the second decade. The single radiographic discriminator from a dentigerous cyst is that the AOT radiolucency extends APICALLY PAST THE CEMENTOENAMEL JUNCTION, enveloping part of the root, and it typically contains faint snowflake flecks of calcification. It is encapsulated and benign, cured by simple ENUCLEATION, and it does not recur.

Note: This is the classic pairing from any radiographic atlas: for a pericoronal radiolucency, ask WHERE IT STOPS. Attached at the CEJ and around the crown only → dentigerous cyst. Extending beyond the CEJ down the root, with flecks, in the anterior maxilla of a teenage girl → AOT. A dentigerous cyst measuring under about 3 mm of follicular space is simply a normal follicle.

Correct answer: B. Calcifying epithelial odontogenic tumour (Pindborg tumour)

• A. Odontogenic myxoma is purely RADIOLUCENT with fine straight septa. It contains no calcified material.
• B. CORRECT. The CALCIFYING EPITHELIAL ODONTOGENIC TUMOUR, or PINDBORG TUMOUR, favours the POSTERIOR MANDIBLE in adults in the fourth to fifth decades and is associated with an unerupted tooth in roughly half of cases. The radiographic hallmark is scattered calcifications of varying size and density within the lucency — the DRIVEN SNOW appearance. Histologically it shows sheets of polyhedral epithelial cells with striking nuclear pleomorphism that does NOT indicate malignancy, prominent intercellular bridges, and amyloid-like material that calcifies in concentric LIESEGANG RINGS and stains with Congo red with apple-green birefringence under polarised light. It is locally invasive, so treatment is local resection with margins rather than simple enucleation, and recurrence runs around 15%.
• C. Ameloblastoma classically produces a multilocular soap-bubble or honeycomb radiolucency of the posterior mandible with marked expansion and knife-edge root resorption — but it does NOT contain scattered internal calcifications.
• D. AOT is a lesion of the ANTERIOR MAXILLA in a young female, encapsulated and cured by enucleation. The age, the site and the behaviour of this lesion all differ.

Note: Two tumours, both associated with an unerupted tooth, both containing calcifications — and separated by everything else. AOT: young female, anterior maxilla, encapsulated, enucleate, no recurrence. CEOT: middle-aged adult, posterior mandible, locally invasive, resect, 15% recurrence.