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Approved by the Cancer.Net Editorial Board, 11/2022

About the gastrointestinal tract

The gastrointestinal (GI or digestive) tract includes the following parts of the body:

  • Esophagus
  • Stomach
  • Gallbladder and bile ducts
  • Liver
  • Pancreas
  • Small intestine
  • Colon
  • Rectum
  • Anus
  • Lining of the gut

The GI tract plays a central role in digesting food and liquid and in processing waste. When you swallow food, it is pushed down a muscular tube called the esophagus and enters the stomach. The muscles in the stomach mix the food and release gastric juices that help break down and digest the food. The food then moves into the small intestine, or small bowel, for further digestion before entering the large intestine. The large intestine helps remove waste from the body. The colon makes up the first 5 to 6 feet (150 to 180 centimeters) of the large intestine. The rectum makes up the last 6 inches (15 centimeters), ending at the anus.

About gastrointestinal stromal tumor (GIST)

A tumor begins when healthy cells change and grow out of control, forming a mass called a tumor. A tumor can be cancerous or benign. A cancerous tumor is malignant, meaning it can grow and spread to other parts of the body. A benign tumor means the tumor can grow but will not spread. A tumor can start in any part of the GI tract. There are several different types of GI tumors, including gastrointestinal stromal tumor (GIST).

GISTs are different from more common types of GI tumors, like colon cancer or stomach cancer, because of the type of tissue in which they start. GISTs belong to a group of cancers called soft-tissue sarcomas. Soft-tissue sarcomas develop in the tissues that support and connect the body. The sarcoma cells resemble the cells that hold the body together, including fat cells, muscles, nerves, tendons, joints, blood vessels, and lymph vessels. You can learn more about the category of soft-tissue sarcoma in a different section on this website.

Research shows that GIST begins in “pacemaker” cells found in the walls of the GI tract. These pacemaker cells are called interstitial cells of Cajal (ICCs), and they send signals to the GI tract to help move food and liquid through the digestive system.