A tumor begins when normal cells change and grow uncontrollably. A tumor can be benign (noncancerous) or malignant (cancerous, meaning it can spread to other parts of the body).

A gastrointestinal stromal tumor (GIST) is a type of tumor that occurs in the gastrointestinal (GI or digestive) tract, including the esophagus, stomach, gallbladder, liver, small intestine, colon, rectum, and lining of the gut. A GIST is different than other, more common types of gastrointestinal tumors because of the type of tissue in which they start. Originally, GISTs were thought to be either muscle or nerve tumors, but recent research shows that GISTs start in cells found in the walls of the GI tract, called interstitial cells of Cajal (ICC). These cells send signals to the GI tract to help move food and liquid through the system.

GISTs belong to a group of cancers called soft tissue sarcoma [2]. Soft tissue sarcomas are a group of cancers that develop in the tissues that support and connect the body, and the sarcoma cells resemble the cells that hold the body together, including fat cells, muscles, nerves, tendons, joints, blood vessels, or lymph vessels.

It is important to note that all GISTs can become cancerous. Sometimes it may be hard for the doctor to tell immediately whether a GIST is likely to come back after its surgical removal. As a result, the doctor will look at many factors to determine the best treatment, including the size of the tumor, whether it has already spread, how many dividing cells there are, and the tumor’s location.

Find out more about basic terms used in this section [3].

Looking for More of an Overview?

If you would like additional introductory information, explore the following related item on Cancer.Net:

• Cancer.Net Patient Education Video [4]: View a short video led by an ASCO expert in sarcoma that provides basic information and areas of research.

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