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A risk factor is anything that increases a person’s chances of getting a disease like cancer. Different cancers have different risk factors. Some risk factors, like smoking, can be changed. Others, like a person’s age or family history, can’t be changed.

But having a risk factor, or even several, does not mean that a person will get the disease. And many people who get the disease may have few or no known risk factors.

Currently, there are very few known risk factors for gastrointestinal stromal tumors (GISTs).

Being older

These tumors can occur in people of any age, but they are rare in people younger than 40 and are most common in people older than 50.

Inheriting certain genetic syndromes

Most GISTs are sporadic (not inherited) and have no clear cause. In rare cases, though, GISTs have been found in several members of the same family. These family members have inherited a gene mutation (change) that can lead to GISTs.

Primary familial GIST syndrome: This is a rare, inherited condition that leads to an increased risk of developing GISTs. People with this syndrome tend to develop GISTs at a younger age than when they usually occur. They are also more likely to have more than one GIST.

Most often, this syndrome is caused by an abnormal KIT gene that is passed from parent to child. This is the same gene that is mutated (changed) in most sporadic GISTs. (See What Causes Gastrointestinal Stromal Tumors?) People who inherited this abnormal gene from a parent have it in all their cells, while people with sporadic GISTs only have it in the cancer cells.

Less often, a change in the PDGFRA gene causes this genetic syndrome. (Defects in the PDGFRA gene are also found in a small percentage of sporadic GISTs.)

Sometimes people with familial GIST syndrome also have skin spots like those seen in patients with neurofibromatosis (discussed below). Before tests for the KIT and PDGFRA genes became available, some of these people mistakenly were thought to have neurofibromatosis.

Neurofibromatosis type 1 (von Recklinghausen disease): This condition is caused by a defect in the NF1 gene. This gene change may be inherited from a parent, but in some cases the change occurs before birth, without being inherited.

People affected by this syndrome often have many benign (non-cancerous) nerve tumors, called neurofibromas, starting when they are young. These tumors form under the skin and in other parts of the body. These people also typically have tan or brown spots on the skin (called café au lait spots).

People with NF1 have a higher risk of GISTs (most often in the small intestine), as well as some other types of cancer.

Carney-Stratakis syndrome: People with this rare inherited condition have an increased risk of GISTs (most often in the stomach), as well as nerve tumors called paragangliomas. GISTs often develop when these people are in their teens or 20s. They are also more likely to have more than one GIST.

This syndrome is caused by a change in one of the SDH (succinate dehydrogenase) genes, which is passed from parent to child.