Therapy Related Changes in Osteosarcoma and Ewing Sarcoma of Bone

Histologic evaluation of neoadjuvant chemotherapy effect is a well-established prognostic indicator in osteosarcoma and Ewing sarcoma arising in bone. Although tumor necrosis is a primary histologic response for the treatment, secondary degenerative changes following necrosis are frequently shown in those tumors. We reviewed some cases of Ewing sarcoma and osteosarcoma of bone with variable histologic alterations after chemotherapy. Secondary degenerative changes seemed to be quite diverse; complete coagulative necrosis, fibrosis/hyalinization, vascular enrichment, edematous stroma, variable shapes of bony trabeculae, and cystic/hemorrhagic changes replaced the tumors. Morphologic changes of the primary tumor cells were not prominent. Such recognition of histologic patterns after chemotherapy would be a great help for the evaluation of therapeutic effect.