Malignant mixed exocrine-endocrine tumor of the pancreas with unusual intracytoplasmic inclusions.

A case of malignant mixed exocrine-endocrine tumor of the pancreas is reported. Electron microscopy revealed abundant neurosecretory granules in most cels. Zymogen granules indicating acinar differentiation were seen in a few cells. Ductal features, including microvilli with prominent filamentous cores and intracytoplasmic mucin granules, were also noted in this lesion. immunocytochemical strains were positive for serotonin and glucagon. Unusual intracytoplasmic fibrillary inclusions are described and their possible origin discussed.