Osteosarcoma mimicking fibrous dysplasia of the jaw

An unusual case of osteosarcoma of the jaw in a 53-year-old man is reported. The tumor primarily occurred in the right maxilla, and spread to the right mandible. Finally, the patient died of an intracranial extension of the tumor after about 4 years. Microscopically, the tumor was well-differentiated osteosarcoma, but was suspected at first to be fibrous dysplasia.