Distinguishing carcinoid tumor from small cell carcinoma of the lung : Correlating cytologic features and performance in the college of American pathologists non-gynecologic cytology program

Abstract Context.—The cytologic features of carcinoid tumor of the lung are well described. Nevertheless, some carcinoids may be difficult to distinguish from small cell carcinomas. Objective.—To correlate the cytologic features of individual cases of carcinoid tumor of the lung in fine-needle aspiration specimens in the College of American Pathologists Non-Gynecologic Cytology Program with the frequency of misclassification as small cell carcinoma. Design.—We reviewed 1100 interpretations from 26 different cases of carcinoid tumor in lung fine-needle aspiration specimens in the College of American Pathologists Non-Gynecologic Cytology Program and correlated the cytologic features with the performance in the program. Results.—Cases were divided into those that were frequently misclassified as small cell carcinoma (at least 20% of the responses, 19 cases) and those that were infrequently misclassified as small cell carcinoma (<10% of all responses, 7 cases). All cases had areas with classic features of car...