Combined ultrastructural, histochemical, and autoradiographic study of osteosarcoma after preoperative chemotherapy according to the COSS 80 protocol.

Twelve osteosarcomas treated according to the COSS 80 protocol (preoperative chemotherapy, resection) were studied by light and electron microscopic, histochemical, and autoradiographic methods. Evidence of regressive and necrotic changes was found in many tumor cells, but the alterations were unspecific. Viable tumor cells of high malignancy were also observed regularly, often at the S phase. As the tumor regression continued, a strong reaction of the mononuclear phagocyte system was manifested by the presence of macrophages and giant cells.