Histologic evaluation of necrosis in osteosarcoma induced by chemotherapy. Regional mapping of viable and nonviable tumor.

The predominant sites of viable and nonviable tumor were determined in the primary lesions of 50 patients with osteosarcoma after initial treatment with preoperative chemotherapy. The degree of tumor destruction was classified as good, fair, and poor and a map of the sites revealing viable and nonviable tumor was constructed. The study revealed several preferential sites where viable tumor was likely to persist: soft tissues, cortex, subcortex, ligaments, and areas in contact with cartilage (growth plate and/or articular cartilage). Localized areas of hemorrhage and necrosis, designated "lacunae," were noted within the tumor. They were frequently surrounded by bundles of viable tumor and appeared to correlate with open surgical biopsies. Factors responsible for this phenomenon and the persistence of viable tumor are discussed. The findings have important implications in the design of surgical treatment and in the use of needle biopsies to determine the effects of preoperative treatment.