Gastrointestinal Stromal Tumors (GISTs)

What are gastrointestinal stromal tumors?

A gastrointestinal stromal tumor (GIST) is a type of tumor that occurs in the gastrointestinal (digestive) tract, most often in the stomach or small intestine. More rarely, it can occur in the colon, rectum, and esophagus. GISTs are a type of soft-tissue sarcoma, which are rare cancers that begin in the tissues that connect, surround, and support other body structures. Tumors occur when genes that regulate normal cell growth are mutated or damaged, which leads to cells growing and dividing at an overaccelerated, unregulated pace. In this case, the tumors are thought to grow from specialized cells in the gastrointestinal tract called insterstitial cells of Cajal (ICCs) or precursors to these cells. These cells are located in the walls of the digestive system and are part of the autonomic nervous system (the part of the nervous system that regulates food digestion). Changes in the DNA of these cells, which control processes like movement of food through the intestines, is what causes a GIST. GISTs most often occur in adults between 40 and 70 years old, but they can rarely occur in younger people. Between 5,000 and 6,000 new cases of GISTs occur each year in the United States. Some of the tumors that appear are benign, which means they are non-cancerous and won’t spread, but others are malignant, which are cancerous and can spread to other body parts. The malignant tumors often spread to sites within the abdominal cavity, the liver, the lungs, and bone.

What are the symptoms of GISTs?

If the tumors are small, they might not cause any signs or symptoms. Those who have larger GISTs usually seek medical attention when they vomit blood or have blood in their stool. Other symptoms include:

• Pain and/or swelling in the abdomen
• A mass that can be seen/felt in the abdominal area
• Nausea and vomiting
• Gastrointestinal bleeding
• Anemia
• Tiredness
• Weakness
• Loss of appetite
• Weight loss
• Difficulty swallowing

What causes GISTs?

Normal, healthy cells grow at a steady rate, and die at a set time. However, sometimes healthy cells develop abnormalities; they grow and multiply at an out of control rate, and take much longer to die. This is what causes cells to accumulate into a tumor. In most cases, GISTs are a result of a spontaneous mutation in a person’s genes, which means that it occurs in people with no family history of the disorder. They usually result from a mutation in either the KIT or PDGFR genes, but some cases come from other mutations that have yet to be identified. Rarely, an inherited genetic mutation causes GISTs. Human traits are inherited from a person’s father and mother; each one contributes a copy of a gene, which interacts with the other copy. This is very uncommon, however.

How are GISTs diagnosed?

GISTs are diagnosed using the following procedures:

• Physical examination that finds a growth in the abdomen
• CT scans
• Upper endoscopy
• Endoscopic ultrasound
• Biopsy

After diagnosis, various imaging tests (CT scans, MRIs, X-rays) are used to find out if the cancer cells have spread to other parts of the body. This is called staging.

What are the stages of GISTs?

Doctors use the information obtained during diagnosis to assign a patient’s cancer a stage. Staging helps determine how serious the cancer is and what the best treatment plan for it is. GIST stages are determined by:

• Tumor size
• Where the tumor first appeared
• Whether the tumor has spread to other parts of the body
• How fast the cancer cells are growing and dividing

What are the treatments for GISTs?

Treatment for GISTs include:

• Surgery
• Targeted drug therapy (with drugs like imatinib)

Other treatment is symptomatic and supportive.

Where can I find out more about GISTs?

• American Cancer Society
• National Organization of Rare Disorders (NORD)
• NIH