Osteosarcoma is a malignant neoplasm of bone. It is among the most common non hematologic primary malignant tumors of bone in both children and adults. The conventional type arises in the intramedullary cavity of the bone and represents 75 % of all osteosarcomas.These tumors penetrate and destroy the cortex of the bone and extend into surrounding soft tissues. In conventional intramedullary osteosarcoma , the predominant histologic pattern may be osteoblastic, fibroblastic, chondroblastic, giant cell rich, malignant fibrous histiocytoma like or partially telangiectatic.
Approximately 85 % of patients with de novo osteosarcoma present before 20 years of age. More than 60 % are in their second decade of life. Males are affected more often than females Osteosarcoma is a chemosensitive tumor specially to high-dose methotrexate. The usual therapy is 8 to 12 weeks pre-operative chemotherapy, followed by conservative surgery or amputation, then by post-operative chemotherapy adapted to the histological response to pre-operative chemotherapy. But, 30 to 40 % of patients have a bad histological response to pre-operative treatment and a worse long term prognosis.