Pancreatic endocrine tumors.

One hundred twenty-five pancreatic endocrine tumors were analyzed by immunocytochemistry using various antisera. Twenty-three of 27 insulinomas, 10 of 10 PP-omas (PP: pancreatic polypeptide) and 15 of 30 "nonsecreting" tumors were benign, whereas 8 of 13 glucagonomas, 16 of 24 gastrinomas, and 16 of 21 VIP-omas (VIP: vasoactive intestinal polypeptide) were malignant. As a rule, the hormone secreted by the tumor and causing clinical symptoms could be localized by immunocytochemistry. Fifty of 95 active tumors were found to contain cells immunoreactive to peptide(s) not causing clinical symptoms, and 54 of 30 "nonsecreting" tumors were shown to be multicellular. By electron microscopy more than one cell type could be identified in 12 tumors. Histologically, the growth pattern of the tumors was very variable and distribution of immunoreactive cells was distinctly patchy. Radioimmunoassay on extracts of 20 of 27 tumors confirmed the presence of peptides visualized by immunocytochemistry. In 17 of 22 specimens, groups of endocrine cells in close contact with ductules were found in the pancreatic parenchyma distant from the tumor. Pancreatic endocrine tumors probably arise from the pancreatic ductular epithelium. They are often multicellular, producing and sometimes secreting more than one hormone or hormone-like substance. They represent highly complex biologic systems in which the interrelationship of various gastrointestinal-pancreatic hormones can be studied.