What Are Gastrointestinal Stromal Tumors?

Cancer starts when cells in the body begin to grow out of control. Cells in nearly any part of the body can become cancer, and can spread to other areas of the body. To learn more about how cancers start and spread, see What Is Cancer?

Gastrointestinal stromal tumors (GISTs) start in special cells in the wall of the gastrointestinal (GI) tract, also known as the digestive tract. To understand GISTs, it helps to know something about the structure and function of the GI tract.

How the gastrointestinal tract works

The gastrointestinal (GI) tract processes food for energy and rids the body of solid waste. After food is chewed and swallowed, it enters the esophagus, a tube that carries food through the neck and chest to the stomach. The esophagus joins the stomach just beneath the diaphragm (the thin band of muscle below the lungs).

The stomach is a sac-like organ that helps the digestive process by mixing the food with gastric juices. The food and gastric juices are then emptied into the small intestine. The small intestine, which is about 20 feet long, continues breaking down the food and absorbs most of the nutrients into the bloodstream.

The small intestine joins the large intestine, the first part of which is the colon, a muscular tube about 5 feet long. The colon absorbs water and mineral nutrients from the remaining food matter. The waste left after this process goes into the rectum as stool (feces), where it is stored until it passes out of the body through the anus.

illustration showing the location of the esophagus, stomach, duodenum, colon, small intestine, cecum, appendix and rectum

Gastrointestinal stromal tumors

Gastrointestinal stromal tumors (GISTs) are uncommon tumors of the GI tract. These tumors start in very early forms of special cells in the wall of the GI tract called the interstitial cells of Cajal (ICCs). ICCs are cells of the autonomic nervous system, the part of the nervous system that regulates body processes such as digesting food. ICCs are sometimes called the “pacemakers” of the GI tract because they signal the muscles in the GI tract to contract to move food and liquid along.

More than half of GISTs start in the stomach. Most of the others start in the small intestine, but GISTs can start anywhere along the GI tract. A small number of GISTs start outside the GI tract in nearby areas such as the omentum (an apron-like layer of fatty tissue that hangs over the organs in the abdomen) or the peritoneum (the layer of tissue that lines the organs and walls of the abdomen).

Some GISTs seem to be much more likely to grow into other areas or spread to other parts of the body than others. Doctors look at certain factors to help tell whether a GIST is likely to grow and spread quickly, such as how large the tumor is, where it's located in the GI tract, and how fast the tumor cells are dividing (its mitotic rate, described in Tests for Gastrointestinal Stromal Tumors).

Other GI tract cancers

It's important to understand that GISTs are not the same as other, more common types of GI tract cancers that develop from other types of cells.

Cancers can occur anywhere in the GI tract − from the esophagus to the anus. Most GI tract cancers, including those of the esophagus, stomach, colon, and rectum, start in the gland cells that line almost all of the GI tract. The cancers that develop in these cells are called adenocarcinomas.

Cancers can also start in squamous cells, which are flat cells that line some parts of the GI tract, like the upper part of the esophagus and the end of the anus. Cancers starting in these cells are called squamous cell carcinomas.

The GI tract also has neuroendocrine cells. These cells have some features in common with nerve cells but other features in common with hormone-producing (endocrine) cells. Cancers that develop from these cells are called neuroendocrine tumors (NETs). These cancers are rare in the GI tract. Carcinoid tumors are an example of a neuroendocrine tumor found in the GI tract.

Other rare types of cancer in the GI tract include different types of soft tissue sarcomas, such as:

  • Leiomyosarcomas: cancers of smooth muscle cells
  • Angiosarcomas: cancers of blood vessel cells
  • Malignant peripheral nerve sheath tumors (MPNSTs): cancers of cells that support and protect nerves

GISTs are different from these other GI tract cancers. They start in different types of cells, need different types of treatment, and have a different prognosis (outlook). This is why doctors need to figure out whether a person with a tumor in the GI tract has a GIST, some other type of cancer, or a non-cancerous condition.

The American Cancer Society medical and editorial content team

Our team is made up of doctors and oncology certified nurses with deep knowledge of cancer care as well as journalists, editors, and translators with extensive experience in medical writing.

American Joint Committee on Cancer. Gastrointestinal stromal tumors. In: AJCC Cancer Staging Manual. 7th ed. New York, NY: Springer; 2010:175-180.

Casali PG, Dei Tos AP, Gronchi A. Chapter 55: Gastrointestinal Stromal Tumor. In: DeVita VT, Lawrence TS, Rosenberg SA, eds. DeVita, Hellman, and Rosenberg’s Cancer: Principles and Practice of Oncology. 10th ed. Philadelphia, Pa: Lippincott Williams & Wilkins; 2015.

Joensuu H, Hohenberger P, Corless CL. Gastrointestinal stromal tumour. Lancet. 2013;382(9896):973-983.

National Cancer Institute. Physician Data Query (PDQ). Gastrointestinal Stromal Tumors Treatment. 2017. Accessed at www.cancer.gov/types/soft-tissue-sarcoma/hp/gist-treatment-pdq on April 17, 2017.

National Comprehensive Cancer Network (NCCN). NCCN Clinical Practice Guidelines in Oncology: Soft Tissue Sarcoma. V.2.2017. Accessed at  www.nccn.org/professionals/physician_gls/pdf/sarcoma.pdf on April 17, 2017.

Last Medical Review: May 17, 2017 Last Revised: May 17, 2017

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