Clinical, computed tomographic, and histopathologic characteristics of juvenile ossifying fibroma with orbital involvement.

A 9-year-old boy who had had painless progressive proptosis of the right eye for 18 months, initially diagnosed as fibrous dysplasia, was found to have a circumscribed mass involving the frontal bone in the roof of the orbit. Biopsy of the mass led to the diagnosis of juvenile ossifying fibroma and the tumor was removed by a craniotomy approach. One year after surgery, the child appeared to be healthy. Ossifying fibroma can sometimes be differentiated from fibrous dysplasia both clinically and by computed tomography. Ossifying fibroma usually appears between the ages of 7 and 28 years and produces slowly progressive proptosis and displacement of the globe in a direction that depends on the original site of the tumor. Fibrous dysplasia usually develops during the first decade of life and produces facial asymmetry, proptosis, and displacement of the globe. An ossifying fibroma characteristically has well-defined margins, is round or ovoid, is usually monostotic, and produces expansion of the involved bone. Fibrous dysplasia is usually sclerotic and expands the bone throughout its length rather than in a localized fashion. Its borders are poorly defined and the lesion is often polyostotic.