Gastrointestinal Stromal Tumors (GIST)

What Are Gastrointestinal Stromal Tumors (GIST)?

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.

Gastrointestinal Stromal Tumors

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

Most people who develop GIST have a mutation in a gene called c-kit, but researchers are not certain how the mutation causes the cancer and the cancer does not always manifest in the same way.

Symptoms of Gastrointestinal Stromal Tumors (GIST)

People with early stage GIST often do not have any symptoms of the disease. Most GISTs are diagnosed after a person develops symptoms. These may include:

  • Abdominal discomfort or pain
  • Vomiting
  • Blood in stools or vomit
  • Fatigue due to anemia (low blood counts)
  • Feeling full after eating only a small amount (early satiety)
  • Loss of appetite

These symptoms may be the result of GIST or of other less serious causes. A person with these symptoms should discuss them with their doctor.

Diagnosing GIST

If a person feels a lump or experiences symptoms that may indicate the presence of a GIST, he or she should discuss them with a doctor. The doctor will take a detailed history of the patient and ask questions about the symptoms.

Scans and tests

Scans and Tests

After a careful physical exam the doctor may perform tests such as an ultrasound, a computed tomography (CT or CAT) scan, or magnetic resonance imaging (MRI) to gain more information about whether there is an abnormal growth, where the growth is located, and whether it has spread.

Biopsy

Biopsy

In some cases a tissue sample, called a biopsy, may be needed. A doctor might perform one of three types of biopsies:

  • Fine needle aspiration
  • Core needle biopsy
  • Excisional or incisional biopsy

After the biopsy is taken, the sample is examined under a microscope by a pathologist. One of the things the pathologist will look for is whether there are detectable amounts of the KIT enzyme. KIT can be identified by looking for a portion of the enzyme called the “CD117” antigen (this is a bit of the enzyme that can be detected by a special diagnostic test). Most GISTs produce KIT, and detection of CD117 (called “expression of CD117” or “CD117 positivity”) helps prove that the growth is a GIST.

After the biopsy is taken, the sample is examined under a microscope by a pathologist. One of the things the pathologist will look for is whether there are detectable amounts of the KIT enzyme. KIT can be identified by looking for a portion of the enzyme called the “CD117” antigen (this is a bit of the enzyme that can be detected by a special diagnostic test). Most GISTs produce KIT, and detection of CD117 (called “expression of CD117” or “CD117 positivity”) helps prove that the growth is a GIST.

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