ABSTRACT

Additionally, tumors are graded with regard to the degree of histologic differentiation with grade 1 being well differentiated and grade 4 being poorly differentiated (46). Ninety-five per cent of extragnathic craniofacial osteosarcomas present with an aggressive histology of grade 3 or 4; however, many authors are not able to clearly correlate a high-grade histology with poorer survival (41,45,48). There are a few commonly named factors that have been reported as significant in the development of osteosarcoma: previous radiation therapy, a history of hereditary retinoblastoma, fibrous dysplasia, and Paget's disease (41,48). Three cases of osteosarcoma of the temporal bone have been reported to arise in areas of previous radiation treatment. One of these occurred in a patient previously treated with 66 Gy for nasopharyngeal carcinoma (43,44). Patients with retinoblastoma have a 500 times increased risk of developing an osteosarcoma during their lifetime, independent of previous radiation treatment to their primary site.