Contributor: Gordon K. Klintworth
Islet cell tumors arise from the islets of Langerhans in the pancreas. This tumor can arise from a variety of cell types and may secrete several hormones. They are rare and account for <10% of all pancreatic tumors. Many are non-functional,  but others secrete specific hormones. Islet cell tumors are a manifestation of multiple endocrine neoplasia syndrome type II. Beta cell tumors account for ~75% of  tumors arising from the islets. Because they may release insulin hypoglycemia is a common finding and the insulin is not regulated by the level of the blood glucose. The pancreatic gastrinoma is an islet cell tumor associated with Zollinger-Ellison syndrome. It consists of  G cells that secrete gastrin. A glucagonoma is a functional that arises from the alpha cell and secretes glucagon. It causes a syndrome characterized by mild diabetes mellitus, anemia, venous thromboses, severe infections, and an erythematous necrotizing migratory rash. Somatostatinoma is a rare tumor arising from the delta cell. It cause mild diabetes mellitus, gallstones, steatorrhea, and hypochlorhydria. D1 cells secrete VIP and cause the Verner-Morrison syndrome. Rare pancreatic islet cell tumors secrete polypeptides. A carcinoid tumor can arise from a enterochromaffin cell in the pancreas. Multiple endocrine neoplasia syndrome type I is frequently associated with Zollinger-Ellison syndrome. Occasionally a variety of  non-pancreatic hormones (ACTH, parathormone, calcitonin, vasopressin) are secreted by islet cell tumors. Cushing syndrome may occur.