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ON THIS PAGE: You will find some basic information about this disease and the parts of the body it may affect. This is the first page of Cancer.Net’s Guide to Carcinoid Tumor. To see other pages, use the colored boxes on the right side of your screen. Think of those boxes as a roadmap to this full guide. Or, click “Next” at the bottom of each page.
About the endocrine system and endocrine tumors
The endocrine system consists of cells that produce hormones. Hormones are chemical substances that are carried through the bloodstream to have a specific regulatory effect on the activity of other organs or cells in the body. Part of the endocrine system is the neuroendocrine system, which is made up of cells that are a cross between traditional hormone-producing cells and nerve cells.
A tumor begins when normal cells change and grow uncontrollably, forming a mass called a tumor. A tumor can be benign or malignant. A benign tumor is not cancerous and usually can be removed without it causing much harm. A malignant tumor is cancerous and can be harmful if not found early and treated. It can spread to and damage the body’s healthy tissues and organs.
An endocrine tumor is a mass that affects the parts of the body that secrete hormones. Because an endocrine tumor develops from cells that produce hormones, the tumor itself can produce hormones and cause serious illness.
About carcinoid tumors
A carcinoid tumor starts in the hormone-producing cells of various organs, mostly in the gastrointestinal tract (such as the stomach and intestines) and the lungs, but it can also start in the pancreas, testicles (in males), or ovaries (in females). More than one carcinoid tumor can occur within the same organ. The cause of carcinoid tumors is unknown.
A carcinoid tumor is a type of neuroendocrine tumor, which means it starts in cells of the neuroendocrine system that make hormones. A carcinoid tumor can make high levels of neuropeptides and amines (hormone-like substances); however, they may not be released in large enough amounts to cause symptoms, or they may be defective and not cause symptoms. A carcinoid tumor can grow slowly for many years without causing symptoms. Although a carcinoid tumor is cancerous, it is often described as "cancer in slow motion."
Here is a general overview of where carcinoid tumors begin:
- 39% occur in the small intestine.
- 15% occur in the rectum.
- 10% occur in the bronchial system of the lungs.
- 7% occur in the appendix.
- 5% to 7% occur in the colon.
- 2% to 4% occur in the stomach.
- 2% to 3% occur in the pancreas.
- About 1% occurs in the liver.
- They rarely occur in ovaries, testicles, and other organs.
There are two subtypes of lung carcinoid tumors: typical and atypical. The difference is based on how a tumor processes and makes serotonin (5-HT, a neurotransmitter involved in behavior and depression):
- A typical lung carcinoid tumor causes high levels of serotonin and chromogranin-A in the blood and high levels of 5-HIAA (a product of serotonin breakdown) in the urine.
- An atypical lung carcinoid tumor has normal levels of serotonin and chromogranin-A in the blood and normal levels of 5-HIAA in the urine but high levels of serotonin and 5-HTP (an amino acid) in the urine, and it can make 5-HTP.
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