Sinonasal psammomatoid ossifying fibromas: CT and MR manifestations.

Five cases of pathologically proved psammomatoid ossifying fibromas of the sinonasal area are presented. All five cases were examined by CT and in three cases MR imaging was performed before and after injection of gadopentetate dimeglumine. The lesions were located in the sphenoethmoidal area and extended over the nasal cavity or orbit in four cases. In one case, the lesion occurred at the perpendicular plate of the ethmoid bone with preservation of the ethmoidal sinus. On CT, all the lesions were expansile and circumscribed by a thick bony wall. Internal septations of bone density (four cases) or enhancing soft-tissue density (one case) were seen and internal content was low in density in all but one from which blood was aspirated. On MR, the bony walls were isointense with gray matter on T1-weighted images and were seen as areas of low intensity on T2-weighted images. The lesions significantly enhanced after injection of contrast material. A well-circumscribed multiloculated expansile mass with a thick wall of bone density on CT scans and enhancement of this area on postcontrast MR images is strongly suggestive of psammomatoid ossifying fibroma.