Background

1. What is a neuroendocrine tumor/carcinoid tumor?

Neuroendocrine tumors arise from the neuroendocrine system, which are composed of cells that have features of both nerve cells and endocrine cells and are found though out the body. These cells share certain biochemical functions such as "amine precursor uptake and decarboxylation (or APUD), hence an earlier classification referred to these tumors as APUDomas. The first neuroendocrine tumor was recognized by a German pathologist by the name of Siegfried Oberndorfer, who in 1907 coined the term "carcinoid" or "carcimona-like", recognizing the relatively low malignant features of this unusual tumor. The term "carcinoid" tumor remains in common use today and refers to a tumor arising from enterochromaffin cells, which are neuroendocrine cells in the gastrointestinal tract. Carcinoids usually secrete serotonin, histamine and other vasoactive substances, which can occasionally cause symptoms of flushing and diarrhea (Carcinoid Syndrome). The other major category of neuroendocrine tumors encompass pancreatic neuroendocrine tumors also sometimes referred to as islet cell tumors, which often secrete any number of pancreatic hormones including gastrin, insulin, VIP, somatostatin, or glucagon whereas about 20-50% of pancreatic neuroendocrine tumors are non-functional.