CT and MRI of congenital sinonasal ossifying fibroma

We report a 9-year-old boy with a sinonasal ossifying fibroma, probably congenital, with atypical findings on CT and MRI. CT revealed a soft-tissue density mass in the sphenoethmoidal sinuses, nasal cavity and right maxillary sinus with a few foci of calcification and with remodelling and destruction of the adjacent facial bones. MRI showed high signal on T2- and intermediate 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 removal was performed. We compare our findings with reports in the literature and discuss the differences from fibrous dysplasia.