A panoramic radiograph of a patient with Gorlin syndrome shows a well-defined radiopaque mass with a surrounding radiolucent rim within the maxillary sinus region. What is the MOST likely diagnosis?

Correct answer: C. Odontoma

• A. An antral pseudocyst is a dome-shaped RADIOLUCENT (soft tissue) swelling on the sinus floor, not a radiopaque mass.
• B. Cementoblastoma is a radiopaque mass FUSED TO A ROOT, most often a mandibular first molar, and typically causes pain — it does not float in the sinus.
• C. Correct. An ODONTOMA is the most common odontogenic tumour — a hamartoma of enamel, dentin, cementum and pulp. Radiographically it is a dense RADIOPACITY with a thin RADIOLUCENT RIM (the follicular space) and a surrounding corticated border. Odontomas are a recognised association of the calcifying odontogenic (Gorlin) cyst.
• D. Osteosarcoma produces an ill-defined, destructive sunburst pattern with symmetrical widening of the PDL space — a very different radiographic picture.

Note: Careful with the word Gorlin: Gorlin-Goltz syndrome (nevoid basal cell carcinoma syndrome) is associated with multiple OKCs, whereas the calcifying odontogenic 'Gorlin' cyst is associated with odontomas. Read the stem's radiographic description, not just the eponym.