Pancreatic endocrine tumor, also known as pancreatic neuroendocrine tumor (PNET), describes a group of endocrine tumors originating in the pancreas that are usually indolent and benign, but may have the potential to be malignant. They can be functional, exhibiting a hormonal hypersecretion syndrome, but can be non-functional presenting with non-specific symptoms and include insulinoma, glucagonoma, VIPoma, somatostatinoma (SSoma), PPoma and Zollinger-Ellison syndrome (ZES, or gastrinoma) and other ectopic hormone producing tumors (such as GRFoma) (see these terms). Epidemiology Prevalence in the U.S. is estimated at 1/4,000-1/3,300 and 1/37,000 in Japan, but this is likely an underestimate due to a low detection rate. Clinical description PNETs, when functional, usually present in the 5th decade of life as various hypersecretion syndromes. These include insulinoma presenting with hyperinsulinemic hypoglycemia; glucagonoma with necrolytic migratory erythema, diabetes mellitus, and thomboembolisms; VIPoma with watery diarrhea, hypokalemia and or hypo/achlorhydia; SSoma with diabetes mellitus, cholelithiasis, steatorrhea and hypochlorhydria; and ZES with severe peptic ulcer disease.