Treated osteosarcoma. Light micrograph showing necrosis of tumour cells in a treated osteosarcoma; however, the osteoid matrix persists. The current treatment protocols for osteosarcoma consist of neoadjuvant chemotherapy followed by surgical resection. Limb-sparing procedures are used whenever feasible. The degree of necrosis following chemotherapy indicates prognosis; the greater the necrosis, the better the prognosis.