[Osteosarcoma].

Osteosarcoma is the most frequent bone tumor in children and young adults. It represents 8% of all tumors in children. Pain and bone tumefaction are the clinical signs. Bone X ray, scintiscan, CT scan and MRN must be done before the biopsy which signs the diagnosis. The best treatment is chemotherapy with high dose methotrexate + leucovorin rescue, adriamycin, cisplatinum and ifosfamide, in different associations followed by surgery either conservative in 80% of the patients or radical. Histologic response to chemotherapy, good or bad responders, is the best prognostic. Postoperative chemotherapy varies with the histologic response; 60 to 70% of patients are living recurrence free at 5 years but metastases could be later.