[Chondromyxoid fibroma: radiologic and radioisotope aspects].

Chondromyxoid fibroma is a relatively rare benign bone tumor whose histologic and radiologic patterns are well known. In this article, we describe a 16-year-old boy with such a tumor in his left tibia. Scintigraphically, this tumor is represented by a "doughnut sign". This aspect, though not pathognomonic, has been reported sporadically in a few diseases: osteoporosis circumscripta cranii, angioblastic meningioma, cranial coccidioidomycosis, and aseptic necrosis of frontal bone. Because of their sites, it is easy to reject these diagnoses in our patient. The most pertinent differential diagnosis with regard to the clinical, radiological, and scintigraphic aspects in the patient is that of a giant cell tumor.