POMC and carcinoid tumor: Recent studies identified expression of high-density and high-affinity VIP receptors in the cellular membranes of the tumors including intestinal adenocarcinomas, carcinoids, small cell lung cancer, mammary duct carcinoma, insulinoma, papillary thyroid carcinoma, melanoma, neuroblastoma, chromophil tumor, and pituitary adenoma secreting adrenocorticotropic hormone (ACTH).