The tumor usually arises in the gastrointestinal tract, anywhere between the stomach and the rectum (the favorite spot is in the appendix) and from there may metastasize (spread) to the liver. In the liver the tumor produces and releases large quantities of serotonin into the systemic bloodstream.
The consequences are called the carcinoid syndrome. It is directly due to the serotonin and includes flushing and blushing, swelling of the face (especially around the eyes), flat angiomas (little collections of dilated blood vessels) on the skin, diarrhea, bronchial spasm, rapid pulse, low blood pressure and tricuspid and pulmonary stenosis (narrowing of the tricuspid and pulmonic valves of the heart), often with regurgitation.
One or more of four kinds of treatment are used for carcinoid tumors: surgery (to take out the cancer); radiation therapy (using high-dose x-rays to kill the cancer cells); biological therapy (using the body's natural immune system to fight the cancer); and chemotherapy (using drugs to kill cancer cells).
Carcinoid tumors are considered a type of endocrine tumor since they secrete a hormone (serotonin). They can occur as part of certain genetic disorders such as the multiple endocrine neoplasia (MEN) type 1 and neurofibromatosis type 1 (NF1 or von Recklinghausen disease).