CT and MRI of congenital sinonasal ossifying fibroma

We report a 9-year-old boy with a sinonasal ossifying fibroma, probably con genital, with atypical findings on CT and MRT. CT revealed a soft-tissue de nsity mass in the sphenoethmoidal sinuses, nasal cavity and right maxillary sinus with a few foci of calcification and with remodelling and destructio n of the adjacent facial bones. MRI showed high signal on T2- and intermedi ate signal on T1-weighted images. A thin, partly enhancing outer shell and some nonenhancing septa were visible on contrast-enhanced images. MRI also showed the tumour to extend into the anterior cranial fossa. Subtotal remov al was performed. We compare our findings with reports in the literature an d discuss the differences from fibrous dysplasia.