[Osteosarcoma].

Osteosarcoma is the most frequent malignant tumor of bones. The peak incidence is in the second decade and the metaphyseal part of long bones is the site of predilection. This tumor is spontaneously rapidly fatal but recent progresses in chemotherapy and surgery have improved its prognosis (for example initial chemotherapy with high dose methotrexate and postoperative chemotherapy adapted to the histological response of the resected tumor to preoperative treatment).