Fine needle aspiration cytology of pulmonary carcinoid tumors.

Twenty-four cases coded as pulmonary carcinoid tumors initially sampled by fine needle aspiration (FNA) biopsy were reviewed in order to determine the cytologic features most useful in making the FNA diagnosis. The diagnosis of carcinoid tumor had been confirmed in 23 cases; the remaining case, though closely resembling a carcinoid tumor on the FNA specimen, proved to be a sclerosing hemangioma of the lung. Comparison of the original and review interpretations of the FNA specimens revealed that all typical spindle cell carcinoids and all atypical carcinoids were correctly diagnosed and classified. Of the 15 typical round cell carcinoids, the original cytologic diagnosis was lymphoma in 2 cases and benign bronchial lining cells in 2 cases. Thus, it appears that diagnostic errors are most likely in "typical" carcinoids. Review of the FNA findings suggests that the frequently stripped cytoplasm (with resulting non-cohesive bare nuclei), coupled with the almost universal plexiform vascularity (seen in 21 of 23 cases), should allow an accurate cytologic diagnosis in virtually all cases.