Duct-acinar-islet cell tumor of the pancreas.

A case of a rare pancreatic tumor, duct-acinar-islet cell tumor is presented. The tumor was incidentally found in the pancreatic body on computed tomography of a 21 year old male suffering from mumps. It was well demarcated from surrounding pancreas, and spherical in shape, measured 2.5 cm in diameter. Histologic and immunohistochemical examinations showed the tumor to consist of three distinct cell populations: duct, acinar and islet cells. Small cell nests consisting of these cellular components, either solely of one cell type or mixed of the three cell types, were separated by broad desmoplastic stroma. Islet (endocrine) cells, which were most predominant, were arranged in a trabecular pattern or small cell nests. Most of them were positive for glucagon, and a few cells expressed insulin, somatostatin, serotonin or pancreatic polypeptide. These cells were distributed randomly within the cell nests. Ducts, some of which contained goblet cells, were found among the endocrine cell nests. Duct-islet complexes were also observed. The acinar cells were the least conspicuous component. They expressed pancreatic alpha-amylase. An electron microscopic examination revealed duct cells with intercellular attachments and interdigitations, endocrine cells containing secretory granules, and acinar cells with zymogen granules. No definite evidence suggesting malignancy could be obtained.