Carcinoid tumors

Carcinoid tumors (neuroendocrine tumors) typically arise anywhere along the GI tract, but they can also be seen in the lungs and elsewhere. Carcinoid tumors are capable of secreting substances that affect vascular, bronchial, and GI smooth muscle tone. Serotonin and histamine are the most commonly secreted hormones, but carcinoid tumors are capable of secreting up to 35 peptides and hormones. Stimuli for the release of these chemical mediators include catecholamines, histamine, hypotension, and tumor manipulation.