presentation of nonpancreatic GI neuroendocrine tumors (carcinoid tumors)
Carcinoid tumors can occur in many different organs throughout the body but most commonly occur in the GI tract (approximately 70% of the time).
Within the GI tract, the most common locations, listed in descending order, are the small intestine, rectum, appendix, large intestine, and stomach. Neuroendocrine tumors of the small intestine are the most likely to cause carcinoid syndrome, which typically does not occur until the patient has developed metastases to the liver.
These tumors frequently result in a desmoplastic (fibrotic) reaction of the adjacent mesentery, causing bowel obstructions. Hindgut carcinoids do not usually produce active hormones and are typically found incidentally during endoscopy performed for other reasons.
Gastric carcinoids are also frequently found incidentally on endoscopy but may cause such symptoms as pain or bleeding.