Gastrointestinal stromal tumors (GISTs) are tumors of the digestive tract that most often occur in the stomach or upper part of the small intestine. GISTs also may be found in the esophagus, large intestine and anus. GISTs occur most often in middle-aged and older adults. GISTs are rare in children. GISTs start in the cells of your digestive tract that send signals that cause digestive organs to contract. These contractions help move food and liquids through your digestive system.

To identify gastrointestinal stromal tumors (GISTs), we perform a comprehensive physical examination. This may include imaging studies of the tumor, blood tests, endoscopy and biopsies.

Imaging studies may include:

• CT scans. CT scans generate detailed cross-sectional images of your body that may show the location and size of your tumor and whether it has spread to other tissues or organs.
• MRI scans. MRI scans use magnetic fields and radio waves to make 3-D images that can reveal abnormalities. Doctors also use MRI scans to determine whether your tumor has spread.
• Positron emission tomography (PET). PET is a noninvasive technique that creates 3-D images of your organs.
• Upper endoscopy. During upper endoscopy, a gastroenterologist or surgeon looks into your esophagus, stomach and small intestine using a thin lighted tube with a small video camera at the tip. Small samples of tissue (biopsies) may be taken if an abnormality is found. A biopsy may not identify GISTs that lie beneath the lining of the gastrointestinal tract, and other tests may be needed.
• Endoscopic ultrasound. During this procedure, an endoscope with an ultrasound probe at the end is passed down your throat and into your stomach and, if necessary, into the upper part of your small intestine. The probe emits high-frequency sound waves that generate images of the inside of your stomach and intestine. This may help reveal a tumor not evident with upper endoscopy alone.

• Removal of the tumor is the primary treatment for GISTs. If your GIST is large or attached to other organs, the surgeon may remove parts of the affected organs.The surgeon may also remove small amounts of tissue outside your GIST to avoid tumor rupture and prevent future obstruction to your digestive tract. You may receive chemotherapy, targeted cell therapy or radiation therapy before surgery to reduce tumor size or after surgery to destroy any remaining cancer cells.
• Targeted therapy. Targeted therapy against an enzyme called tyrosine kinase treats your tumor by working against genetic changes that cause GISTs. Imatinib is the most common of these therapies.If your tumor is too large or invasive to be removed with surgery, your doctor may use targeted therapy to shrink the tumor enough to make surgery possible. If your tumor is removed, your doctor may recommend targeted therapy to reduce the risk of recurrence.
• Radio frequency ablation (RFA). During RFA, your doctor inserts a thin needle guided by ultrasound or CT scan into your tumor and generates heat to destroy cancer cells. You may receive RFA if you have several tumors or liver tumors that can’t be removed, or to relieve symptoms of GISTs such as pain.