Duct-acinar-islet cell tumor of the pancreas.

Two cases of pancreatic tumor consisting of duct, acinar, and islet components are reported. Both tumors measured about 1.0 cm in diameter and were without definite fibrous encapsulation. Histologic, immunocytochemical, and electron microscopic studies revealed three distinct cell populations: duct, acinar, and islet cells. Both endocrine and exocrine components were seen within the same cell nest. Islet components predominated in both cases. Nearly all the cells in the islet component were positive for insulin. Few cells positive for glucagon, somatostatin, or pancreatic polypeptide were present within the tumor cell nests. Duct cells were the least conspicuous cellular element of the tumor; they were positive for mucin and immunoreactive for cytokeratin and carcinoembryonic antigens (CEA). The acinar component was the minor element of the tumor in both cases. Electron microscopic study also confirmed three different cell populations in the tumor: duct cells arranged in a ductal structure with intercellular attachments and microvilli, islet cells containing beta granules, and acinar cells with zymogen granules. The tumors presented herein indicate that both their endocrine and exocrine components might have been derived from a common precursor. The implication and significance of the differentiation of different cells within the same tumor is discussed in relation to the concept of an amine precursor uptake and decarboxylation (APUD) system.