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Gastrointestinal Stromal Tumors (GIST)

What GIST Is

Gastrointestinal stromal tumors (GISTs) are rare tumors that start in special cells found in the wall of the GI tract, called the interstitial cells of Cajal (ICCs). ICCs are part of the autonomic nervous system, and coordinate the automatic movements of the GI tract. ICCs are sometimes called the "pacemakers" of the GI tract because they send signals to the muscles of the digestive system, telling them to move food and liquid through the GI tract.

GISTs may occur anywhere along the length of the digestive tract from the esophagus to the anus. 

GIST is slightly more common in men. Although GISTs are most often diagnosed in people 50 years of age or older, they can occur in any age group. GIST appears to occur with increased frequency in patients with a history of neurofibromatosis (NF1 disease).

Approximately 50 to 70 percent of all GISTs develop in the stomach, while around 20 to 30 percent will arise in the small intestine. The rest arise in the esophagus, colon, and rectum. 

Why GIST Develops

The way in which GIST grows, or the route the tumor takes when it spreads through the body, is called its pathophysiology.

Scientists are beginning to unravel some of the processes that go on inside cells that cause them to develop into GISTs. Normally these cells, like other cells in the body, grow and divide in a controlled fashion. But sometimes things can go wrong, allowing these cells to grow out of control and ultimately become cancerous.

Scientists have discovered that cells may grow in an uncontrolled manner as the result of an abnormality in their DNA. In GIST, a specific mutation causes a cellular enzyme known as KIT to be switched "on" all the time. KIT is an enzyme (called a "tyrosine kinase") responsible for sending growth and survival signals inside the cell. If it is ON, the cell stays alive and grows or proliferates. The overactive, uncontrolled mutant KIT enzyme triggers the runaway growth of GIST tumor cells. This insight into the way GISTs develop has already helped to identify new treatments for this sarcoma.

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