Pancreatic neuroendocrine neoplasms

Abstract

Neuroendocrine neoplasms that arise from the neuroendocrine cells of the pancreas, the islets of Langerhans, include well-differentiated neuroendocrine tumors (NETs) that are clinically classified as functioning and nonfunctioning. Functioning tumors are associated syndromes due to excess insulin, glucagon, somatostatin, and/or pancreatic polypeptide, but they can also secrete gastrin, vasoactive intestinal peptide, or serotonin. Aggressive tumors can produce ectopic hormones such as ACTH, GHRH, GH, vasopressin, and/or parathyroid hormone-related peptide causing Cushing's syndrome, acromegaly, SIAD, and hypercalcemia. Nonfunctioning tumors are more common and are usually diagnosed because of mass effects or the presence of metastases. The morphology of these tumors is highly variable, and they are graded based on their proliferative activity. They frequently arise in patients with hereditary predisposition syndromes. Poorly differentiated neuroendocrine carcinomas (NECs), subclassified as small cell or large cell variant, are high-grade malignancies that have a distinct biology and require a different therapeutic approach. Mixed neuroendocrine and non-neuroendocrine neoplasms (MiNENs) are composite lesions composed of different types of non-neuroendocrine neoplasms, including adenocarcinomas or squamous cell carcinomas, along with various grades of NET or with poorly differentiated NEC.