Odontogenic Cysts & Tumors MCQ

Radiolucencies and radiopacities of the jaws are a category of their own, because the teeth and their developmental tissues produce cysts and tumors found nowhere else in the body. Four questions read almost any jaw lesion: Is the related tooth vital or non-vital? Where does the lesion sit relative to the tooth (at the apex, around the crown, or on the lateral root)? Is it unilocular or multilocular? And, because imaging is never definitive, what does the biopsy show?

Odontogenic and Developmental Cysts

• The radicular (periapical) cyst is the most common odontogenic cyst. It is inflammatory, arises from epithelial rests of Malassez at the apex of a non-vital tooth, and a residual cyst is one left behind after the tooth is removed.
• The dentigerous cyst surrounds the crown of an unerupted or impacted tooth and attaches at the cementoenamel junction, classically on a mandibular third molar; the eruption cyst is its soft tissue counterpart over an erupting tooth.
• The odontogenic keratocyst favors the posterior mandible and ramus, behaves aggressively with a high recurrence rate, and when multiple should prompt evaluation for Gorlin (nevoid basal cell carcinoma) syndrome.
• The lateral periodontal cyst sits along the lateral root surface (mandibular premolar and canine region), and the nasopalatine duct cyst is a non-odontogenic developmental cyst of the midline anterior maxilla, classically a heart-shaped radiolucency, with the adjacent incisors vital.

Odontogenic Tumors

• The odontoma is the most common odontogenic tumor and is a hamartoma (a disorganized overgrowth, not a true neoplasm): the compound type forms multiple small tooth-like denticles, and the complex type forms a disorganized calcified mass; either can block eruption.
• The ameloblastoma is benign but locally aggressive, classically a multilocular soap-bubble or honeycomb radiolucency in the posterior mandible; it arises from odontogenic epithelium, does not form enamel, and recurs unless removed with an adequate margin.
• The adenomatoid odontogenic tumor (AOT) is the 'two-thirds tumor' (about two-thirds in young females, in the anterior maxilla, associated with an impacted canine) and can mimic a dentigerous cyst; the calcifying epithelial odontogenic tumor (Pindborg) shows amyloid and calcifications (a driven-snow appearance).
• The odontogenic myxoma shows a fine 'tennis racket' or 'step ladder' trabecular pattern, and the cementoblastoma is a radiopaque mass fused to the root of a vital tooth with a thin radiolucent rim.

Reading the Radiolucency: Principles

• Pulp vitality reframes the differential: a periapical radiolucency on a non-vital tooth is usually inflammatory (cyst or granuloma), while the same finding on a vital tooth points elsewhere (for example, early periapical cemento-osseous dysplasia).
• A periapical (radicular) cyst and a periapical granuloma cannot be reliably distinguished on a radiograph alone; size is only a rough guide, and definitive distinction is histologic.
• Unilocular versus multilocular matters: a multilocular (soap-bubble or honeycomb) radiolucency raises ameloblastoma, keratocyst, and myxoma, whereas many cysts are unilocular.
• Imaging narrows the differential but is never diagnostic on its own; biopsy and histopathology give the diagnosis, so a jaw lesion is not finalized on the radiograph.