Gastrointestinal tumors: Gastrointestinal tissue tumor (GIST) is a rare cancer. It is a type of soft tissue sarcoma . Before 1998, doctors classified the gastrointestinal tract as leiomyosarcoma, gastrointestinal angiosarcoma (GANT), or a combination of these two types of tumors. Gastrointestinal tumors -GISTs- are often found during an endoscopy or CT scan for an unrelated condition. When people with GIST have some symptoms, the tumor beging to be large. Most gastrointestinal infections occur in the digestive tract, often in the stomach, but they can also occur in other parts of the intestine. Gastrointestinal tumors have the potential to spread to other parts of the body.