[Fibrous dysplasia and ossifying fibroma. 2 unusual fibro-osseous lesions of the paranasal sinuses].

Fibrous dysplasia and ossifying fibroma are locally destructive and deforming benign lesions that can occur anywhere in the craniofacial skeleton, including the paranasal sinuses. Differentiation between these two diseases is essential because of their differing natural histories, and distinctions must be made by correlating clinical information with radiological and histological findings. The cases of fibrous dysplasia and ossifying fibroma described in this report illustrate the subtle differences between these two fibroosseous lesions. Emphasis is placed on the differing natural history and management of these two unusual lesions in order to expedite aggressive treatment when required.