Multicentric osteosarcoma: clinicopathologic and radiographic study of 56 cases.

Multicentric osteosarcoma (M-OGS) is characterized by multicentricity of osseous osteosarcomas, either synchronous or metachronous, without visceral involvement. The study's purpose was to clinicopathologically and radiographically analyze 56 cases of M-OGS (22 synchronous and 34 metachronous). The distal femur was the most common site. Histologically, all tumors were high grade. Of 22 patients with synchronous M-OGS, 16 had 3 or more simultaneous tumors; the axial skeleton was involved in 14 (64%) of 22 cases. In metachronous M-OGS, the second malignancy occurred after a median of 22 months. Treatment was surgery, chemotherapy, radiotherapy, or a combination of these. Patients with metachronous osteosarcoma had a median survival longer than did patients with synchronous tumors. Overall, 8 long-term survivors were treated by aggressive surgery with wide margins (plus chemotherapy and/or radiotherapy). M-OGS combines multiple skeletal locations of high-grade conventional osteosarcomas and has a poor prognosis. Aggressive surgery may result in improved long-term survival, particularly in patients with metachronous disease.