Gastrointestinal stromal tumor can be found in any area of the gastrointestinal (GI) track such as esophagus, stomach, pancreases, large intestine, small intestine and appendix. Small GISTs often do not cause symptoms, and are usually discovered incidentally on upper GI endoscopy or computer tomography. Large GISTs may cause abdominal discomfort / pain, or even GI bleeding.