What is a gastrointestinal stromal tumor (GIST)?

Cancer starts when cells change (mutate) and grow out of control. The changed (abnormal) cells often grow to form a lump or mass called a tumor. Cancer cells can also grow into (invade) nearby areas. They can spread to other parts of the body, too. This is called metastasis.

A gastrointestinal stromal tumor (GIST) is a rare tumor in the gastrointestinal (GI) or digestive tract. The tumor starts in cells called the interstitial cells of Cajal (ICCs). ICCs are part of the nervous system. They coordinate the automatic movements of the GI tract. ICCs are sometimes called the "pacemakers" of the GI tract because they send signals to the muscles of the digestive system, telling them to move food and liquid through the GI tract.

Most GISTs start in the stomach or small intestine. But they can form anywhere along the digestive tract from the esophagus to the anus.

Scientists are beginning to unravel some of the processes that go on inside cells that cause them to develop into a GIST. Normally these cells, like other cells in the body, grow and divide in a controlled fashion. But sometimes things go wrong. This lets these cells grow out of control and ultimately become cancer.

Scientists have discovered that cells grow in an uncontrolled manner as the result of a defect (mutation) in their DNA. In most GISTs, a specific gene defect causes the cells to make too much of an enzyme called KIT. KIT is an enzyme called a tyrosine kinase. It's responsible for sending growth and survival signals inside the cell. If the gene to make KIT is "on," the cell stays alive and grows in number. The overactive, uncontrolled mutant KIT gene sets off the runaway growth of GIST cells.

Much less often, GIST cells make too much of a different protein called PDGFRA. This protein can also cause the cells to grow. These insights into the way a GIST develops have already helped to find new treatments.

Who is at risk for a gastrointestinal stromal tumor?

A risk factor is anything that may increase your chance of having a disease. The exact cause of someone’s cancer may not be known. But risk factors can make it more likely for a person to have cancer. Some risk factors may not be in your control. But others may be things you can change.

The risk factors for a GIST include:

• History of neurofibromatosis type 1, also known as von Recklinghausen disease

• Being male

• Age 50 or older

• Rare inherited syndromes, such as Carney-Stratakis syndrome

• Family history of GISTs

Talk with your healthcare provider about your risk factors for a GIST and what you can do about them.

Can a gastrointestinal stromal tumor be prevented?

At this time, there is no screening test to check for a GIST. Still the earlier any tumor is found and treated, the better the chance of survival. For this reason, if you notice possible signs or symptoms of a GIST, discuss them with your healthcare provider right away.

What are the symptoms of a gastrointestinal stromal tumor?

People with an early-stage GIST often don’t have any symptoms of the disease. Most GISTs are diagnosed after you develop symptoms. These may include:

• Belly (abdominal) discomfort or pain

• A lump or mass in the belly that you can feel

• Vomiting

• Blood in stools or vomit

• Fatigue because of low red blood cell counts (anemia) caused by bleeding

• Feeling full after eating only a small amount (early satiety)

• Loss of appetite or weight loss

Many of these may be caused by other health problems. But it is important to see your healthcare provider if you have these symptoms. Only a healthcare provider can tell if you have cancer.

How is a gastrointestinal stromal tumor diagnosed?

If your healthcare provider thinks you may have a GIST, you will need certain exams and tests to be sure. Your healthcare provider will ask you about your health history, your symptoms, risk factors, and family history of disease. They will also give you a physical exam. You may also have one or more of these tests:

• Endoscopy. This test uses a thin, lighted tube with a tiny video camera on the end that is passed down the throat. The healthcare provider can see inside the stomach through this tube.

• Imaging tests, such as a CT scan or MRI scan. These tests create detailed images that may be done to look for an abnormal growth. They can show where the growth is and whether it has spread.

• Biopsy. A biopsy is the only way to confirm cancer. Small pieces of tissue are taken out from the tumor. They are looked at at a lab to see if cancer cells are present. Your healthcare provider might get biopsy samples during the endoscopy. In other cases, they may take a sample by putting a thin, hollow needle through the skin and into the tumor, or take a sample during surgery.

After the biopsy, the tissue sample is looked at under a microscope by a healthcare provider called a pathologist. One of the things the pathologist will test for is the KIT enzyme. Most GISTs make KIT, also called CD117. Finding KIT is called expression of CD117 or CD117 positivity. This helps prove that the growth is a GIST. If CD117 is not found, the sample may be tested for the PDGFRA protein. 

After a diagnosis of GIST, you may need other tests. These help your healthcare providers learn more about your cancer. They can help determine the stage of the cancer. The stage is how much and how far the cancer has spread (metastasized) in your body. It is one of the most important things to know when deciding how to treat the cancer.

Once your cancer is staged, your healthcare provider will talk with you about what the stage means for your treatment. Be sure to ask your healthcare provider to explain the stage of your cancer to you in a way you can understand. 

How is a gastrointestinal stromal tumor treated?

A GIST grows differently in each person. The size and location of the tumor and the rate that it grows are important in figuring out the risk the tumor presents. The risk for spread to other parts of the body (metastasis) can vary a lot.

It can be hard to tell a noncancerous (benign) tumor from cancer (malignant). But most experts agree that all GISTs have some risk for malignant behavior. In some cases, even a small tumor that is not growing rapidly may spread. The location of the tumor seems to affect the tumor's behavior. When a GIST metastasizes it usually spreads to the liver or the lining of the abdominal wall.

What are gastrointestinal stromal tumor treatment side effects?

It's important to know which medicines you're taking. Write your medicines down, and ask your healthcare team how they work and what side effects they might have.

Talk with your healthcare providers about what signs to look for and when to call them. For example, imatinib can cause itchy skin rashes that can lead to infections. Make sure you know what number to call with questions. Is there a different number for evenings, holidays, and weekends?

It may be helpful to keep a diary of your side effects. Write down physical, thinking, and emotional changes. A written list will make it easier for you to remember your questions when you go to your appointments. It will also make it easier for you to work with your healthcare team to make a plan to manage your side effects.

Coping with a gastrointestinal stromal tumor

Many people feel worried, depressed, and stressed when dealing with cancer. Getting treatment for cancer can be tough on the mind and body. Keep talking with your healthcare team about any problems or concerns you have. Work together to ease the effect of cancer and its symptoms on your daily life.

Make sure to:

• Talk with your family or friends.

• Ask your healthcare team or social worker for help.

• Speak with a counselor.

• Talk with a spiritual advisor, such as a minister or rabbi.

• Ask your healthcare team about medicines for depression or anxiety.

• Keep socially active.

• Join a cancer support group in person or online.

Cancer treatment is also hard on the body. To help yourself stay healthier, try to:

• Eat a healthy diet with as many protein foods as possible.

• Drink plenty of water, fruit juices, and other liquids.

• Keep physically active.

• Rest as much as needed.

• Talk with your healthcare team about ways to manage treatment side effects.

• Take your medicines as directed by your team.

When should I call my healthcare provider?

Your healthcare provider will talk with you about when to call. You may be told to call if you have any of the below:

• New symptoms or symptoms that get worse

• Signs of an infection, such as a fever

• Side effects of treatment that affect your daily function or don't get better with treatment

Ask your healthcare provider what signs to watch for and when to call. Know how to get help after office hours and on weekends and holidays. 

Key points about GIST

• A gastrointestinal stromal tumor (GIST) is a rare tumor in the digestive tract.

• Most GISTs start in the stomach or small intestine. But they can form anywhere along the digestive tract from the esophagus to the anus.

• The risk factors for a GIST include having neurofibromatosis type 1, being male, and a family history of GISTs

• People with an early-stage GIST often don’t have any symptoms of the disease.

• You may have an endoscopy, CT scan, MRI, or biopsy to confirm the diagnosis.

• Treatment may be done with surgery and targeted therapy medicine.

Next steps

Tips to help you get the most from a visit to your healthcare provider:

• Know the reason for your visit and what you want to happen.

• Before your visit, write down questions you want answered.

• Bring someone with you to help you ask questions and remember what your provider tells you.

• At the visit, write down the name of a new diagnosis, and any new medicines, treatments, or tests. Also write down any new instructions your provider gives you.

• Know why a new medicine or treatment is prescribed, and how it will help you. Also know what the side effects are and when they should be reported.

• Ask if your condition can be treated in other ways.

• Know why a test or procedure is recommended and what the results could mean.

• Know what to expect if you do not take the medicine or have the test or procedure.

• If you have a follow-up appointment, write down the date, time, and purpose for that visit.

• Know how you can contact your healthcare provider if you have questions, especially after office hours or on weekends.