A rare cause of exophthalmos: cemento-ossifying fibroma.

Cemento-ossifying fibroma is a benign fibroosseous lesion that contains fibrous tissue and calcified tissue resembling bone, cementum or both. It is frequently seen in the mandibula and maxilla, but it may rarely affect the ethmoid sinus. In this report, we presented computed tomography findings of an ossifying fibroma of the ethmoid sinus associated with exophthalmos. A 25-year-old woman presented with complaints of exophthalmos, headache, and nasal congestion of six-month history. Physical examination showed a firm mass on the right side of the nasal septum and right-sided exophthalmos. Eye movements, vision, and the fundus were normal. Axial and coronal computed tomography scans showed a well-delineated, round mass, 4x4.5x3 cm in size, in the right ethmoid sinus, extending from the right orbital rim to the right nasal cavity. Near-total excision of the mass was performed by a lateral rhinotomy and medial maxillotomy approach. Based on histologic and radiological findings, the diagnosis was made as ossifying fibroma.