Tumor

• Carcinoid cancer is caused by carcinoid tumors that over-produce and circulate serotonin around the body via the bloodstream. Serotonin is a natural chemical messenger for the body.
  
  

The Body

• Cancer causing carcinoid tumors are usually found in the stomach, small intestine, appendix, colon, rectum and in rare cases in the ovaries. The symptoms become noticeable once it reaches the gastrointestinal tract.
  
  

The Liver

• The liver is the main filter for the body fighting organ. When the tumor metastasizes to the liver, the over-produced hormones are then transferred from the blood stream to the tissues, in a rapid manner.
  
  

The Lung

• Carcinoid tumors can also affect the lungs which increases the risk of cancer. Tumors of the lung cause cancer as they pass chemicals directly into the bloodstream without allowing the liver to degrade the chemicals created by the tumors.
  
  

Family History

• A family history of a rare condition called Multiple Endocrine Neoplasia type 1 (MEN1) increases the risk of carcinoid cancer. Cancer Research UK reports that 1 in 10 people with carcinoid cancer also have the condition MEN1.
  
  

Associated Condition

• The rare condition neurofibromatosis also increases the risk of contracting carcinoid cancer according to Cancer Research UK.