[Pathogenesis of endocrine tumors of the pancreas].

Precise pathohistologic and immunohistochemical investigations of the pancreas in elderly autopsy cases revealed that endocrine tumors are found very frequently. Some endocrine tumors of the pancreas may originate from Langerhans islets, although other endocrine tumors may develop from endocrine cells or stem cells with multiple differentiation ability and occur in the duct cells or acinar cells. This possibility may be supported by the evidence that ductular or tubular structures were found in or adjacent to tumors in about 60% of minute tumors and that hormone production was found in both duct cells and acinar cells based on immunohistochemical findings. The occurrence of ductuloinsular tumors, acinar endocrine cell tumors, and duct-acinar-islet cell tumors may also support these observations. Islets of Langerhans with diameter of 500 microm or greater, or islets with a mean +/- 2 SD or greater, were found around the tumors, suggesting the presence of factors that promote the growth of islets of Langerhans. Molecular biological investigations will further analyze the pathogenesis of endocrine tumors of the pancreas. There are three possible origins of endocrine tumors of the pancreas: Langerhans islets cells, ductular cells, and acinar cells.