Gastrointestinal Stromal Tumor (GIST)
Gastrointestinal stromal tumors (GIST) are rare, soft tissue sarcomas that occur
between the muscle layers of the GI tract. About 5,000 new cases of GIST occur
in the U.S. each year. This is 0.2% of all GI cancers.
Common Sites of GIST
ξ Stomach (40% - 70%)
ξ Small intestine (20% - 40%)
ξ Colon and rectum (5% - 15%)
ξ Esophagus (less than 5%)
What is GIST?
GIST begins when a kit gene in the center (nucleus) of a cell has a defect
(mutation). The kit gene makes a protein, called KIT, which is found on the
surface of the cell. The KIT protein is part of a system that makes a cell divide and
grow. When the kit gene mutates, the KIT protein becomes too active. It signals
the cell to grow and divide without stopping and with no turn off. The cell divides
out of control forming a tumor. Mutations in kit are found in 90 – 95% of GISTs.
GIST may grow slowly and remain stable for years. Or, it may progress quickly,
spreading (metastasizing) to other organs. GISTs are typed as low, intermediate,
or high risk. The typing is based on their size, the rate at which they divide, and
GIST occurs most often in adults between the ages of 40 and 80. The mean age at
first diagnosis is 63. It occurs slightly more often in men than women. There are
no known risk factors. There is a small increase in risk if someone in your family
has had the disease.
Small GISTs are often found when the patient has a routine test or procedure for
some other problem. There may be no warning symptoms. Larger tumors may
cause pain, nausea, vomiting, loss of appetite, weight loss, bloating, early feelings
of fullness, fatigue, or bleeding.
The best ways to predict chance of recovery are the size of the tumor and rate at
which the cell divides.
Diagnosis and Staging
These tests and procedures may be used to diagnose GIST and decide the stage of
disease or extent of the cancer. The stage of the disease is a key part in making a
ξ Physical exam and complete health history.
ξ Blood tests – looking for anemia and liver or kidney functions.
ξ CT scan (CAT scan) – detailed picture of the inside of the body taken by a
special x-ray machine that is attached to a computer.
ξ MRI (magnetic resonance imaging) – an x-ray exam that uses a magnet,
radio waves, and a computer to make detailed pictures of the inside of the
ξ PET scan (positron emission tomography) – Tumor cells use a lot of energy.
PET scans show sites of high energy. They are often used to find cancer that
has spread to other parts of the body.
ξ Endoscopy – a procedure performed by a doctor who specializes in GI tract
diseases. A small, lighted tube (scope) is passed through the mouth,
esophagus, and into the stomach. Tissue samples (biopsy) can be taken and
looked at under the microscope to check for cancer.
ξ Biopsy – cells or tissues are removed to be looked at under the microscope
to check for cancer. Tissue can be removed during an endoscopy or surgery,
or CT or ultrasound guidance. Special stains are needed to detect KIT,
which is present in 90-95% of all GIST patients.
Stages of GIST
Staging is a way to describe a cancer in terms of size, location, and whether it has
spread to other tissues or organs.
Very Low Risk – Smaller than 2 cm, less than 5/50 HPF (high-powered field)
Low Risk – 2 cm to 5 cm, less than 5/50 HPF
Intermediate Risk – Larger than 5 cm, 6 to 10/50 HPF
5 cm to 10 cm, Less than 5/50 HPF
High Risk – More than 5 cm, More than 5/50 HPF
More than 10 cm, any mitotic rate
Any size, more than 10/50 HPF
Surgery is the main treatment for GIST tumors that have not spread. GISTs rarely
spread to lymph nodes, so lymph nodes do not need to be removed. Surgery may
also be used after treatment with a targeted therapy to shrink the tumor, making
GIST tumors tend not to respond to radiation treatments. Sometimes, radiation
may be used to treat symptoms of a lesion which has spread.
Usual chemotherapy treatment has little effect on GISTs. Targeted therapies called
selective tyrosine kinase inhibitors have been used to disrupt the abnormally active
Clinical trials may be offered at our Cancer Center. Ask your doctor how you can
take part in these trials to help find new and better treatments for people with
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have any questions. If this information was not given to you as part of your care, please check with your doctor. This
is not medical advice. This is not to be used for diagnosis or treatment of any medical condition. Because each
person’s health needs are different, you should talk with your doctor or others on your health care team when using
this information. If you have an emergency, please call 911. Copyright © 4/2015 University of Wisconsin Hospitals
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