A post-chemotherapy specimen of an osteosarcoma showing areas of sclerotic osteoid with cell dropout in between trabeculae of medullary bone. At the present time, there is no consensus on how much tumor should be examined to assess the response to preoperative chemotherapy. Many institutions examine an entire slab of the tumor. Another unresolved question is how to accurately estimate viable tumor volume when scattered foci of viable tumor cells are found in a necrotic background. With neoadjuvant chemotherapy, the long-term survivial for osteosarcoma involving extremities is reported to be as high as 75% to 80%. Tumors involving the axial skeleton have worse prognosis. The unfavorable prognostic indicators include young age, large tumor, poor response to preoperative chemotherapy involvement of axial skeleton, shorter duration of symptoms, male sex, and high alkaline phosphatase levels.