[A case of multicentric intraosseous well differentiated osteosarcoma originating in the rib].

We have experienced a rare case of multicentric intraosseous well differentiated osteosarcoma originating in the left 7th and 9th rib. A 35-year-old man was admitted to our hospital with slowly growing mass of the left chest wall. From radiographic appearance the mass was suspected multicentric tumor of bone originating from the left 7th and 9th rib, and from needle biopsy the mass was suspected giant cell tumor of bone. Tumors were completely resected en bloc, and chest wall defect was covered with Marlex mesh. Pathological diagnosis was multicentric intraosseous well differentiated osteosarcoma originating in the left 7th and 9th rib. At 8 months after operation, the patient is doing well and there is no evidence of recurrence and lung metastasis.