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 Throat and Esophagus The throat (pharynx—see also Throat) lies behind and below the mouth. When food and fluids leave the mouth, they pass through the throat. Swallowing of food and fluids begins voluntarily and... read more , stomach Stomach The stomach is a large, bean-shaped, hollow muscular organ consisting of three regions: Cardia Body (fundus) Antrum (See also Overview of the Digestive System.) read more , or intestines. Most gastrointestinal stromal tumors 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 Small Intestine The duodenum is the first segment of the small intestine, and the stomach releases food into it. Food enters the duodenum through the pyloric sphincter in amounts that the small intestine can... read more , and a small percentage occurs in the esophagus, colon Large Intestine The large intestine consists of the Cecum and ascending (right) colon Transverse colon Descending (left) colon Sigmoid colon (which is connected to the rectum) read more , and rectum Rectum and Anus The rectum is a chamber that begins at the end of the large intestine, immediately following the sigmoid colon, and ends at the anus (see also Overview of the Anus and Rectum). Ordinarily, the... read more .
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 gastrointestinal stromal tumors at a later time. These tumors usually grow slowly, but some can grow more rapidly and spread to other sites (metastasize).
Symptoms
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.
Diagnosis
Endoscopy or colonoscopy
Imaging tests
A doctor may use an endoscope or colonoscope (a flexible viewing tube—see Endoscopy Endoscopy Endoscopy is an examination of internal structures using a flexible viewing tube (endoscope). Endoscopy can also be used to treat many disorders because doctors are able to pass instruments... read more ) 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 (see Video Capsule Endoscopy Video Capsule Endoscopy Video capsule endoscopy (wireless video endoscopy) is a procedure in which the person swallows a battery-powered capsule. The capsule contains one or two small cameras, a light, and a transmitter... read more ) can also be used to show tumors of the small intestine, but this technique does not allow the doctor to do a biopsy.
To determine whether the cancer has spread to other organs, doctors do a computed tomography Computed Tomography and Magnetic Resonance Imaging of the Digestive Tract Computed tomography (CT—see also Computed Tomography (CT)) and magnetic resonance imaging (MRI—see also Magnetic Resonance Imaging (MRI)) scans are good tools for assessing the size and location... read more (CT) scan of the abdomen or endoscopic ultrasonography Ultrasound Scanning (Ultrasonography) of the Abdomen Ultrasound scanning uses sound waves to produce pictures of internal organs (see also Ultrasonography). An ultrasound scan can show the size and shape of many organs, such as the liver and pancreas... read more 
(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).
Treatment
Surgical removal
If the cancer has not spread to other organs, doctors remove it surgically.
If the cancer has spread, doctors often treat it with a certain type of chemotherapy drug (imatinib). If imatinib does not help, doctors may give other chemotherapy drugs such as sunitinib and regorafenib.
Another drug called avapritinib can be given to people who have gastrointestinal stromal tumors that cannot be treated with surgery or that have spread to other parts of the body and that are caused by a genetic mutation called PDGFRA exon 18.
