Histological evaluation of the nodules resected in the treatment of pulmonary metastatic disease.

During an 18 month period, 41 patients who had previously had a primary tumor removed, underwent 60 operations for resection of newly detected radiographic pulmonary nodules. Primary tumors included 16 osteogenic sarcomas, 9 malignant melanomas, 12 soft tissue sarcomas, 1 Ewing's sarcoma, 2 adenocarcinomas of the rectum, and 1 testicular teratocarcinoma. One hundred and eight-one pulmonary specimens were submitted for pathologic examination and 149 discrete nodules were found in these specimens by the pathologist (83%). Metastases represented 76-100% of nodules removed in 68% of the operations, 51-75% of nodules in 12%, 26-50% of nodules in 14%, and less than 25% of nodules in 6% of the cases. Metastatic disease was found in 90% of cases where nodules were greater than or equal of 0.5 cm in diameter, while metastases were found in on 33% of cases where the largest nodules removed were less than 0.5 cm. In only two cases did the histology of the pulmonary metastases differ from that of the primary tumor. We conclude that although benign lesions cannot be distinguished from metastases except by resection, nodules less than 0.5 cm in diameter probably should be observed for a further increase in size prior to operation.