A gastrointestinal stromal tumor, also called a GIST, is a type of cancer that begins in the digestive system. GISTs happen most often in the stomach and small intestine.

A GIST is a growth of cells that's thought to form from nerve cells in the walls of the digestive organs. The nerve cells play a part in the process that moves food through the body.

Small GISTs may cause no symptoms. And GISTs may grow so slowly that they don't cause problems at first. As a GIST grows, it can cause symptoms that may include belly pain and nausea.

GISTs can happen in people at any age, but they are most common in adults and very rare in children. The cause of most GISTs isn't known.

Symptoms

Gastrointestinal stromal tumor symptoms include:

• A growth in the belly area.
• Belly pain.
• Fatigue.
• Nausea and vomiting.
• Not feeling hungry when you would expect to.
• Feeling full if you eat only a small amount of food.
• Dark-colored stools caused by bleeding in the digestive system.

When to see a doctor

Make an appointment with a doctor or other healthcare professional if you have any symptoms that worry you.

Causes

The cause of a gastrointestinal stromal tumor often isn't known. This cancer, which also is called a GIST, happens in the digestive system. It most often affects the stomach and small intestine. GISTs are thought to begin in nerve cells in the walls of the digestive organs. These nerve cells play a part in the process that moves food through the body.

A GIST starts when nerve cells in the digestive system develop changes in their DNA. A cell's DNA holds the instructions that tell the cell what to do. In healthy cells, the DNA gives instructions to grow and multiply at a set rate. The instructions tell the cells to die at a set time. In cancer cells, the DNA changes give different instructions. The changes tell the cancer cells to grow and multiply quickly. Cancer cells can keep living when healthy cells would die. This causes too many cells.

The cancer cells might form a mass called a tumor. The tumor can grow to invade and destroy healthy body tissue. In time, cancer cells can break away and spread. When cancer spreads, it's called metastatic cancer.

Risk factors

Risk factors for gastrointestinal stromal tumor, also called GIST, include:

• Family history. People with a family history of GISTs may be at increased risk of this cancer.
• Hereditary syndromes. People with some conditions that run in families may be more likely to have GISTs. Examples include neurofibromatosis type 1 and Carney-Stratakis syndrome.
• Adult age. A GIST can happen at any age. This cancer happens most often in adults. It's rare in children.

Diagnosis

To diagnose a gastrointestinal stromal tumor, your healthcare professional might start by asking you about your symptoms and your health. This cancer, which also is called a GIST, happens in the digestive system.

If symptoms suggest that you may have a GIST, you might need other tests to find the cancer. These tests may include:

• Imaging tests. Imaging tests help your healthcare team find your tumor and see its size. Tests might include ultrasound, CT, MRI and positron emission tomography (PET) scans. Not everyone needs every test.
• Upper endoscopy. This test uses a long, thin tube (endoscope) with a light on the end. The tube goes through the mouth and down the throat. This test looks at the inside of the esophagus, stomach and the first part of the small intestine.
• Endoscopic ultrasound (EUS). This test also uses an endoscope, but with an ultrasound probe on the tip of the scope. The ultrasound probe uses sound waves to make pictures of the tumor and show its size.

• Fine-needle aspiration biopsy. This test collects a small sample of tissue from the tumor so it can be tested in a lab. This test is like EUS, but with a thin, hollow needle on the tip of the endoscope. The EUS finds the tumor. The needle collects small amounts of tissue for the lab tests.

  Sometimes the needle can't get enough cells, or the results aren't clear. You might need surgery to collect the sample.

• Laboratory tests on biopsies. The biopsy sample from your tumor goes to a lab for testing. In the lab, specialists test the cells to see if they're cancer cells. Other tests give your healthcare professional details about your cancer cells that are used to plan your treatment.

Treatment

Gastrointestinal stromal tumor treatment often involves surgery and targeted therapy. Which treatments are best for you depends on your situation. This cancer, which also is called a GIST, happens in the digestive system.

Some GISTs don't need treatment right away. Very small GISTs that don't cause symptoms might not need treatment. Instead, you might have tests to see if the cancer grows. If your GIST grows, you can start treatment.

Surgery

The goal of surgery is to remove all the GIST. It's often the first treatment for GISTs that haven't spread to other parts of the body.

Surgery might not be used if your tumor grows very large or if it grows into nearby structures. If this happens, your first treatment might be targeted therapy to shrink the tumor. You might have surgery later.

The type of operation you have depends on your cancer. Often surgeons can access the GIST using minimally invasive surgery. This means surgical tools go through small cuts in the abdomen rather than through one large cut.

Targeted therapy

Targeted therapy for cancer is a treatment that uses medicines that attack specific chemicals in the cancer cells. By blocking these chemicals, targeted treatments can cause cancer cells to die. For GISTs, the target of these medicines is an enzyme called tyrosine kinase that helps cancer cells grow.

Targeted therapy for GISTs often begins with imatinib (Gleevec). Targeted treatments can be given:

• After surgery to lower the risk that the cancer will come back.
• Before surgery to shrink the tumor and make it easier to remove.
• As the first treatment if the cancer has spread to other parts of the body.
• If the GIST comes back.

Other targeted therapy medicines might be used if imatinib doesn't work for you or if it stops working. Targeted therapy is an active area of cancer research, and new medicines are likely to become options in the future.

Preparing for an appointment

Make an appointment with a doctor or other healthcare professional if you have any symptoms that worry you. If your health professional thinks that you might have a gastrointestinal stromal tumor, that person may refer you to a specialist. Often, this is a doctor who specializes in cancer, called a medical oncologist.

Appointments can be short and being prepared can help. Here's some information that may help you get ready.

What you can do

When you make the appointment, ask if there's anything you need to do in advance, such as fasting before having a specific test. Make a list of:

• Your symptoms, including any that seem unrelated to the reason for your appointment.
• Key personal information, including major stresses, recent life changes and family medical history.
• All medicines, vitamins or other supplements you take, including the doses.
• Questions to ask your healthcare professional.

Take a family member or friend along, if possible, to help you remember the information you're given.

For gastrointestinal stromal tumors, some basic questions to ask your healthcare professional include:

• Do I have cancer?
• Do I need more tests?
• What are my treatment options?
• What are the potential risks of these treatment options?
• Do any of the treatments cure my cancer?
• Can I have a copy of my pathology report?
• How much time can I take to consider my treatment options?
• Are there brochures or other printed materials that I can take with me? What websites do you recommend?
• What would happen if I chose not to have treatment?

Don't hesitate to ask other questions.

What to expect from your doctor

Your healthcare professional is likely to ask you several questions, such as:

• When did your symptoms begin?
• Have your symptoms been continuous or occasional?
• How severe are your symptoms?
• What, if anything, seems to improve your symptoms?
• What, if anything, appears to worsen your symptoms?