FIBROUS DYSPLASIA AND CEMENTO-OSSIFYING FIBROMA - A HISTOLOGIC SPECTRUM

Fibrous dysplasia (FD) and cemento-ossifying fibroma (COF) are benign fibro-osseous lesions that are generally considered to be separate ent ities, distinguished by histologic and radiographic features. In our e xperience, some lesions lack the classic clinical, radiographic, or pa thologic features of FD or COF and rather have overlapping features of both entities. Consequently, these cases are frequently diagnosed non specifically as fibro-osseous lesions. We examined 56 gnathic and extr a-gnathic fibro-osseous lesions of bone morphologically, clinically, a nd radiographically to determine whether they can be reliably distingu ished and whether their distinction has any clinical or prognostic sig nificance. The lesions exhibited a broad morphologic spectrum of patte rns ranging from pure FD (24 cases) to pure COF (10 cases). Twenty-two lesions contained a mixture of both patterns; 11 lesions with a predo minant FD pattern contained calcified spherules histologically indisti nguishable from those characteristically seen in COF. The remaining 11 lesions contained areas of typical FD adjacent to areas of COF. The l esions examined also demonstrated considerable radiographic overlap, a nd FD could not be reliably distinguished from COF. The recurrence rat e was low for all lesions regardless of the histologic pattern. Becaus e of histologic and radiographic overlap and similar low recurrence ra te of FD and COF, we consider them to be related lesions, and COF is p robably an opposing end of a morphologic spectrum of FD.