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	Carcinoid Cancer

	Carcinoid cancer and related neuroendocrine tumors (NETs) are small, slow growing tumors found mostly in the gastrointestinal system, but can be in other parts of the body such as the pancreas and the lung. Since most of these grow very slowly, compared to other cancers, it usually takes many years before they become sizable or cause symptoms.
	Carcinoid tumors can produce an excess of hormonelike substances, such as serotonin, bradykinin, histamine, and prostaglandins. Excess levels of these substances can sometimes result in a diverse set of symptoms called carcinoid syndrome.
	When carcinoid tumors occur in the digestive tract or pancreas, the substances they produce are released into a blood vessel that flows directly to the liver (portal vein), where enzymes destroy them. Therefore, carcinoid tumors that originate in the digestive tract generally do not produce symptoms unless the tumors have spread to the liver.
	Common sites:
	39% small intestine 26% appendix 15% rectum 10% bronchial system of the lungs 5-7% colon 2-4% stomach 2-3% pancreas >1% liver