Gastrointestinal stromal tumors (GISTs) are cancerous (malignant) tumors that develop from a specific kind of cell (mesenchymal precursor cells) within the wall of the esophagus, stomach, or intestines. Most GISTs are caused by a mutation in a gene called C-KIT that controls the growth of cells. Most (60 to 70%) of these tumors occur in the stomach, 20 to 25% occur in the small intestine, and a small percentage occurs in the esophagus, colon, and rectum.
The average age at diagnosis is 50 to 60. People who have had radiation therapy to the abdomen for the treatment of other tumors can develop GISTs at a later time. These tumors usually grow slowly, but some can grow more rapidly and spread to other sites (metastasize).
Symptoms of gastrointestinal stromal tumors depend on the location of the tumor but include abdominal pain, bleeding, indigestion, and a feeling of fullness after eating a small meal. Nausea and vomiting can occur if the tumor has grown large enough to block the digestive tract.
A doctor may use an endoscope or colonoscope (a flexible viewing tube—see Endoscopy) to locate the tumor and do a biopsy (remove a tissue sample for examination under a microscope). A wireless battery-powered capsule that contains one or two small cameras can also be used to show tumors of the small intestine; however, this techniques does not allow biopsies.
To determine whether the cancer has spread to other organs, doctors do a computed tomography (CT) scan of the abdomen or endoscopic ultrasonography (in which an ultrasound probe is placed on the tip of the endoscope and shows the lining of the digestive tract more clearly than many other tests).
If the cancer has not spread to other organs, doctors remove it surgically. If the cancer has spread, doctors often treat with a certain type of chemotherapy drug (imatinib).