Cytologic features of islet-cell tumors.

Although a number of reports have demonstrated the accuracy of fine needle aspiration (FNA) in the diagnosis of nonendocrine pancreatic carcinomas, the cytomorphology of islet-cell tumors (pancreatic endocrine tumors) is not well defined. This paper describes the cytologic features of three histologically confirmed cases of islet-cell tumors. The three tumors occurred in one man and two women, who were 63, 64 and 70 years of age, respectively. Each patient underwent FNA of pancreatic mass with computed body tomography guidance. The aspirates contained large numbers of tumor cells in two cases and a smaller number in one case. The cells, distributed singly and in small groups, were small and round or polygonal, with scant to more often abundant, dense or granular cytoplasm. The nuclei were often located eccentrically and were round to oval, with smooth nuclear borders and finely stippled chromatin. Many nuclei contained a single nucleolus. Multinucleated cells were present and generally contained two or three nuclei. Although the diagnosis of islet-cell tumors in fine needle aspirates is difficult, the cytomorphologic features of these tumors are sufficiently distinctive to suggest the diagnosis, especially when a relatively monomorphic population composed predominantly of single cells is present.