Fine-needle aspiration cytology of idiopathic pancreatic islet cell adenosis.

A 68-yr-old woman was hospitalized because of abdominal pain, an enlarged pancreatic head by CT, and a questionable 4-cm mass in the liver. Fine-needle aspiration (FNA) of the pancreatic head disclosed a highly cellular specimen consisting of clusters of cytologically bland, monotonous, small nuclei and variable but generally sparse cytoplasm. Because of the differentiated monomorphic character of the cell clusters, the postaspiration differential cytopathologic diagnosis included islet cell tumor, acinic cell tumor, carcinoid, lymphoma, and well differentiated ductal adenocarcinoma. Pancreaticoduodenectomy and hepatic biopsy yielded a grossly normal pancreas and a cirrhotic liver. Histologic examination of the pancreas revealed a spotty but extensive spectrum of islet changes ranging from normal to bland hyperplasia, nesidioblastosis, microadenosis, and neuroendocrine microadenomas, all appearing in a light and electron microscopic context of an otherwise normal pancreas. This case highlights the differential diagnostic ambiguities presented by a continuum of pancreatic islet cell proliferations, especially among patients in whom there are no known predisposing factors for such diffuse preneoplastic or neoplastic changes.