Neuroendocrine (Carcinoid) Tumor
Neuroendocrine tumors comprise a diverse group of malignancies and, as a broad definition include gastrointestinal neuroendocrine tumors as well as pheochromocytoma, thyroid cancer, and even small cell lung cancer. Gastrointestinal neuroendocrine tumors are tumors that arise within the lining of the gastrointestinal tract that include the stomach, small intestine, appendix and large intestine. They are usually subclassified as either pancreatic neuroendocrine tumors or carcinoid tumors. The term karzinoide was used by Oberndorfer in 1907 to describe similar tumors that appeared to behave in a more indolent (slow growing) fashion than typical adenocarcinomas. Carcinoid tumors have also been seen to arise in a wide range of organs but most commonly involve the lungs, bronchi, and gastrointestinal tract.
Neuroendocrine cells produce hormones that help regulate digestive juices and the muscles used in moving food through the stomach and intestines. A gastrointestinal carcinoid tumor may also produce hormones. Pancreatic neuroendocrine tumors can be non functional (do not produce any hormones) or produce hormones such as insulin (commonest), gastrin (second most common) or glucagon, vasoactive intestinal polypeptide, or somatostatin (less common). Pancreatic tumors that produce these hormones are named after the predominant hormone they secrete (insulinoma, gastrinoma, glucagonoma etc). Carcinoid tumors that start in the rectum usually do not produce hormones.
