Small cell squamous and mixed small cell squamous--small cell anaplastic carcinomas of the lung.

Five patients are presented who had neoplasms which, by light microscopy and in two cases cytologically, appeared to be small cell anaplastic (polygonal and fusiform cell type) carcinomas of the lung. However, by electron microscopy, four of the carcinomas exhibited squamous characteristics including desmosomes and tonofilament bundles, and lacked demonstrable neurosecretory granules, suggesting that they were small cell squamous carcinomas. The fifth carcinoma contained cells with neurosecretory granules as well as cells demonstrating squamous differentiation. One patient died within 3 months of presentation. Three patients survived for approximately 18 months each; two received chemotherapy but one was treated by surgical resection alone. The fifth patient had a peripheral coin lesion which was treated by surgical resection only; he is alive without evidence of recurrent carcinoma 1 year after operation. We suggest that some carcinomas of the lung with the light-microscopic and cytologic appearance of small cell anaplastic carcinoma are actually small cell variants of squamous cell carcinoma and lack the characteristic neurosecretory granules of classic small cell carcinoma. The behavior of these tumors needs to be determined.