Psammomatoid ossifying fibroma in the extraconal space: a case report.

A 24-year-old patient with left eye proptosis and intermittent pain for 5 months was admitted to our hospital. Physical examination revealed neither extra ocular muscle limitations nor visual field defects. Magnetic resonance imaging (MRI) revealed a multicystic mass in the left extraconal space compressing the superior oblique muscle and adjacent frontal lobe. Layered hemorrhage was observed within the lesion in the 1-month follow-up MRI. Dynamic contrast enhanced imaging showed mild increased perfusion of the surrounding peripheral portion. Magnetic resonance spectroscopy showed an increased lactate/lipid peak of 1.3 ppm. Combined open and endonasal surgery was performed, and the final diagnosis was psammomatoid ossifying fibroma. The tumor was positive for vimentin, and negative for smooth muscle actin, S100 and epithelial membrane antigen. Despite its rarity, psammomatoid ossifying fibroma should be considered when multicystic lesions with peripheral enhancement near the orbit exhibit progressive inner hemorrhage.