Aneurysmal bone cyst secondary to ossifying fibroma in the orbit.

A 28-year-old man presented with proptosis and medial displacement of the right eye, intermittent pain, and diplopia of 1 month's duration. Radiologic examination demonstrated a mass in the right lateral orbit resembling an aneurysmal bone cyst (ABC). Histopathologic evaluation of the surgically excised lesion via orbitotomy confirmed the radiologic diagnosis. Two months later, the patient presented again with a mass at the same location as the previous one, with a major component that was solid. The recurrent lesion was excised via frontal craniotomy. Histopathologic examination of the surgical specimen led to a diagnosis of ABC secondary to trabecular ossifying fibroma. During the follow up of 13 months, the lesion did not recur. To the best of the authors' knowledge, this is the first case of ABC secondary to ossifying fibroma in the orbit. ABC can dominate the radiologic appearance of the lesion and veil the primary neoplasm.