Morphology of pulmonary metastases from osteosarcoma during chemotherapy.

Osteosarcoma is known to metastasize rather early, and even after surgical resection of the primary metastases may occur predominantly in the lung. Administration of polychemotherapy for destruction of micrometastases has served to improve prognosis. Preoperative chemotherapy facilitates the evaluation of regression, another factor of high prognostic relevance. Morphologic analysis of pulmonary metastases developing during chemotherapy is of considerable interest on account of the potential therapy resistance of certain histologic subtypes of osteosarcoma. In the present study pulmonary metastases resected in 20 thoracotomies of 15 osteosarcoma patients were investigated by light microscopy and compared, if possible, to the respective primaries. All patients had received chemotherapy, predominantly according to the COSS 80 and COSS 82 protocols. The histologic picture of a tumor was found to change from the primary to the pulmonary metastasis, a pattern also verified in the lung metastases collected in consecutive thoracotomies from the same patient. Several different subtypes were regularly found side by side in the metastases, but generally no special sensitivity or resistance to chemotherapy could be attributed to any of these subtypes. Our results nevertheless do indicate an increased resistance of anaplastic tumor tissue. The response to chemotherapy agreed in 9 of 10 primaries with that of their metastases.