Gastrointestinal stromal tumor is a disease in which abnormal cells form in the tissues of the gastrointestinal tract.

The gastrointestinal (GI) tract is part of the body’s digestive system. It helps to digest food and takes nutrients (vitamins, minerals, carbohydrates, fats, proteins, and water) from food so they can be used by the body. The GI tract is made up of the following organs:

• Stomach.
• Small intestine.
• Large intestine (colon).

Some gastrointestinal stromal tumors (GISTs) grow slowly over time and may never cause a problem for a patient, while others can grow and spread very quickly. They are most common in the stomach and small intestine but may be found anywhere in or near the GI tract. Some scientists believe that GISTs begin in cells called interstitial cells of Cajal (ICC), in the wall of the GI tract.

See the PDQ summary about Childhood Gastrointestinal Stromal Tumors Treatment for information on the treatment of GIST in children.

Genetic factors can increase the risk of having a gastrointestinal stromal tumor.

Anything that increases your risk of getting a disease is called a risk factor. Having a risk factor does not mean that you will get cancer; not having risk factors doesn't mean that you will not get cancer. Talk with your doctor if you think you may be at risk.

The genes in cells carry the hereditary information received from a person’s parents. The risk of GIST is increased in people who have inherited a mutation (change) in a certain gene. In rare cases, GISTs can be found in several members of the same family.

GIST may be part of a genetic syndrome, but this is rare. A genetic syndrome is a set of symptoms or conditions that occur together and is usually caused by abnormal genes. The following genetic syndromes have been linked to GIST:

• Neurofibromatosis type 1 (NF1).
• Carney triad.

Signs of gastrointestinal stromal tumors include blood in the stool or vomit.

These and other signs and symptoms may be caused by a GIST or by other conditions. Check with your doctor if you have any of the following:

• Blood (either bright red or very dark) in the stool or vomit.
• Pain in the abdomen, which may be severe.
• Feeling very tired.
• Trouble or pain when swallowing.
• Feeling full after only a little food is eaten.

Tests that examine the GI tract are used to diagnose gastrointestinal stromal tumors.

The following tests and procedures may be used:

• Physical exam and health history: An exam of the body to check general signs of health, including checking for signs of disease, such as lumps or anything else that seems unusual. A history of the patient’s health habits and past illnesses and treatments will also be taken.
• CT scan (CAT scan): A procedure that makes a series of detailed pictures of areas inside the body, taken from different angles. The pictures are made by a computer linked to an x-ray machine. A dye may be injected into a vein or swallowed to help the organs or tissues show up more clearly. This procedure is also called computed tomography, computerized tomography, or computerized axial tomography.
• MRI (magnetic resonance imaging): A procedure that uses a magnet, radio waves, and a computer to make a series of detailed pictures of areas inside the body. This procedure is also called nuclear magnetic resonance imaging (NMRI).
• Endoscopic ultrasound and biopsy: Endoscopy and ultrasound are used to make an image of the upper GI tract and a biopsy is done. An endoscope (a thin, tube-like instrument with a light and a lens for viewing) is inserted through the mouth and into the esophagus, stomach, and first part of the small intestine. A probe at the end of the endoscope is used to bounce high-energy sound waves (ultrasound) off internal tissues or organs and make echoes. The echoes form a picture of body tissues called a sonogram. This procedure is also called endosonography. Guided by the sonogram, the doctor removes tissue using a thin, hollow needle. A pathologist views the tissue under a microscope to look for cancer cells.

If cancer is found, the following tests may be done to study the cancer cells:

• Immunohistochemistry: A laboratory test that uses antibodies to check for certain antigens (markers) in a sample of a patient’s tissue. The antibodies are usually linked to an enzyme or a fluorescent dye. After the antibodies bind to a specific antigen in the tissue sample, the enzyme or dye is activated, and the antigen can then be seen under a microscope. This type of test is used to help diagnose cancer and to help tell one type of cancer from another type of cancer.
• Mitotic rate: A measure of how fast the cancer cells are dividing and growing. The mitotic rate is found by counting the number of cells dividing in a certain amount of cancer tissue.

Very small GISTs are common.

Sometimes GISTs are smaller than the eraser on top of a pencil. Tumors may be found during a procedure that is done for another reason, such as an x-ray or surgery. Some of these small tumors will not grow and cause signs or symptoms or spread to the abdomen or other parts of the body. Doctors do not agree on whether these small tumors should be removed or whether they should be watched to see if they begin to grow.

Certain factors affect prognosis (chance of recovery) and treatment options.

The prognosis and treatment options depend on the following:

• How quickly the cancer cells are growing and dividing.
• The size of the tumor.
• Where the tumor is in the body.
• Whether the tumor can be completely removed by surgery.
• Whether the tumor has spread to other parts of the body.