Carcinoid tumor

The cause of carcinoid tumors is currently unknown. There are some unavoidable risk factors that may increase a person's risk of developing the tumor. It is important to note that people with several risk factors may never develop cancer, while others with no risk factors may develop cancer. Possible risk factors for carcinoid tumors include:^[1][2][3]

• Family history of multiple endocrine neoplasia type 1 (MEN1). About 10% of gastrointestinal (GI) carcinoid tumors are thought to be associated with MEN1.
• Family history of neurofibromatosis type 1 (NF1).
• Family history of other genetic syndromes such as tuberous sclerosis complex and von Hippel Lindau disease.
• Other stomach conditions. People with diseases that damage the stomach and reduce stomach acid levels (in particular, pernicious anemia) have a greater risk of developing stomach carcinoid tumors.
• Race and gender. GI carcinoid tumors are more common among African Americans than among white people, and slightly more common among women than men. Lung carcinoid tumors are more common among white people than among people of other ethnicities.

Carcinoid tumors generally have been considered to be sporadic, except for a small proportion which occur as a part of multiple endocrine neoplasia (MEN) syndromes. Carcinoid tumors most notably may occur in MEN1, and occasionally in MEN2.^[4] These conditions are caused by mutations in the MEN1 and RET genes, respectively, and most cases are considered to have an autosomal dominant pattern of inheritance.^[5] When associated with these familial syndromes, carcinoids are more likely to develop in the foregut, especially in the thymus and lung.^[4]

It has been reported that even when a carcinoid tumor does not appear to be associated with MEN, there does appear to be an increased risk for developing a carcinoid tumor among first-degree relatives; this suggests that some carcinoid tumors may be familial. However, little data are available on the percentage of individuals with a carcinoid tumor that have a family history of carcinoid tumors.^[4]