Fine needle aspiration cytology of carcinoid tumors

OBJECTIVE: To define the cytomorphologic features of carcinoid tumor. STUDY DESIGN: The study consisted of 19 carcinoid turners sampled by fine needle aspiration. These included 6 pulmonary carcinoids, 11 intestinal carcinoids and 2 aspirates from a patient with a mediastinal carcinoid. The cytomorphologic features of carcinoid tumor were documented, and, in selected cases, immunocytochemical findings were noted. Additionally, the cytology literature concerning carcinoid tumor was reviewed and summarized. RESULTS: Morphologically, the carcinoid tumors consisted predominantly of loose groups with a background of single cells. A striking degree of cellular and nuclear monomorphism was seen in all cases. Nuclei were small and round to oval, and all exhibited a characteristic finely granular, evenly distributed chromatin pattern. Cytoplasm was minimal to moderate in amount and finely granular in appearance. Necrosis and prominent nucleoli were not seen. Positive staining was noted in all seven cases in which immunostaining for chromogranin was performed. Neuron-specific enolase was positive in four of five cases. CONCLUSION: The cytomorphologic characteristics of carcinoid tumors are distinctive, and appropriate ancillary studies can assist in confirming the diagnosis.