Periosteal osteosarcoma of the jaws: report of 2 cases.

Osteosarcoma (OS) occurs most often in the long bones. OS of the jaws has clinical and biologic aspects different from those of the long bones. They tend to occur at an older mean age, pain and swelling are more typical, and prognosis is more favorable. Nearly all OS shows a very prominent central intramedullary bone component. Only rarely are juxtacortical (peripheral) OS located in the jaws. There are 2 main types of juxtacortical OS, periosteal and parosteal. We present 2 cases of OS of the jaws where the clinical, radiologic, and histologic findings pointed to a diagnosis of periosteal OS. Both patients presented, in fact, with lesions located superficially on the bone surface with no marrow involvement. Both tumors were characterized by the presence of a moderately differentiated chondroblastic tumor with foci of osteoid and bone formation. Periosteal OS should be differentiated microscopically from periosteal chondrosarcoma, intramedullary OS with periosteal extension, high-grade surface OS, and parosteal OS. The clinical differential diagnosis was done, in these cases, for epulis, gingival tumors, peripheral odontogenic fibroma, peripheral ossifying fibroma, pyogenic granuloma, peripheral giant cell granuloma, and mesenchymal malignant tumors.