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Unformatted text preview: 614 Arch Pathol Lab MedVol 129, May 2005 Carcinoid Tumor Versus Small Cell Carcinoma Renshaw et al 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 Andrew A. Renshaw, MD; Jennifer Haja, CT(ASCP); Richard L. Lozano, MD; David C. Wilbur, MD; for the Cytology Committee, College of American Pathologists 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 indi- vidual cases of carcinoid tumor of the lung in fine-needle aspiration specimens in the College of American Patholo- gists Non-Gynecologic Cytology Program with the fre- quency of misclassification as small cell carcinoma. Design. We reviewed 1100 interpretations from 26 dif- ferent cases of carcinoid tumor in lung fine-needle aspi- ration specimens in the College of American Pathologists Non-Gynecologic Cytology Program and correlated the cy- tologic features with the performance in the program. Results. Cases were divided into those that were fre- quently misclassified as small cell carcinoma (at least 20% of the responses, 19 cases) and those that were infrequent- ly misclassified as small cell carcinoma ( , 10% of all re- sponses, 7 cases). All cases had areas with classic features of carcinoid tumor. Cases were reviewed independently by 3 cytopathologists specifically looking for cytologic fea- tures that might be responsible for misclassification as small cell carcinoma. All 7 cases that were infrequently misclassified consisted of numerous monotonous well-pre- served tumor cells that were either entirely round or were a mixture of round and spindle-shaped cells. Six of 7 cases showed a prominent streaming vascular pattern with tu- mor cells attached to the endothelial cell core. In contrast, cases that were frequently misclassified had 1 of 6 patterns that were not seen in cases that were rarely misclassified. These 6 patterns were: (1) poorly preserved and pale-stain- ing cells with fine chromatin and a suggestion of molding (5 cases); (2) numerous large, well-preserved, spindle- shaped cells (2 cases); (3) numerous cells varying markedly in both size and shape (both round and spindle-shaped cells), with a common finding of degenerated, smudgy, small round and spindle-shaped cells (9 cases); (4) hypo- cellular specimens (8 cases); (5) obscuration of cells by blood (2 cases); and (6) tumor cells present predominantly in groups, with few isolated cells (8 cases). In none of these cases were mitoses or true necrosis identified....
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