Diagnosis
If you have any of the above symptoms, your doctor should conduct a physical exam, take your medical history, and ask you about your risk factors and family history to determine what might be causing them. If your doctor suspects a GIST, he or she may order the following tests to diagnose the disease.
Physical Examination
A doctor will perform a physical examination to keep track of your level of health and how treatment may be affecting with you as well as how you are coping with the treatment's possible side effects. A doctor should perform an exam to look for liver enlargement, a possible sign GIST has invaded your liver, as well as any indication of fluid in the abdomen, possibly indicating involvement of the lining of the gut.
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Upper endoscopy
The doctor uses an endoscope, a flexible, narrow tube with a camera and light on the end, to examine the lining of the esophagus, stomach, and small intestine and look for any irregularities. If the doctor notices an area of abnormal tissue, he will use the endoscope to take a tissue sample for a biopsy.
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Upper gastrointestinal (GI) series
This test is also referred to as a barium swallow. The patient drinks a chalky liquid called barium and undergoes a series of X-rays. The barium covers the inside layer of the esophagus, stomach, and small intestine and clearly outlines it on the X-rays, making it easy for the doctor to identify any abnormalities. You may also need a barium enema, in which your doctor gives the barium through your anus, and takes a series of X-rays to examine your colon and rectum.
Colonoscopy
Your doctor uses a colonoscope (narrow, flexible tube with a camera and light on the end) to examine the inner lining of your large intestine for any abnormalities. Your doctor may also remove a tissue sample for biopsy during this procedure.
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Endoscopic ultrasound (EUS)
For this procedure, the surgeon uses an endoscope with an ultrasound device at the end of the tube. This device sends out high-frequency sound waves to make images of the GI tract, and allows the doctor to see how deep the tumor has grown into the wall and whether it has invaded the lymph nodes. Ultrasound may also allow a more accurate biopsy.
Complete blood count (CBC)
A CBC measures the levels of a person's blood cells, including red blood cells, white blood cells, platelets, neutrophils, and hemoglobin. Your doctor may order a CBC to check for anemia (low red blood cells), which can be caused by internal bleeding related to GIST tumors. Other blood work like a comprehensive metabolic panel is also done to check for organ function and rule out liver function abnormalities.
Fecal Occult Blood Test (FOBT)
Your doctor performs this test to check for any signs of blood in the stool. Bloody stools may be a symptom of GISTs and may be caused by other cancer in your digestive tract, as well as a variety of benign conditions. Your doctor will collect a stool sample and analyze it biochemically.
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Bone Scan
A bone scan uses a radioactive substance to identify cancerous tissues in the bones. A bone scan provides a picture of all of the bones in the body, and allows doctors to detect small areas of cancer cells not visible on plain X-rays. The radioactive substance collects in these areas and illuminates them on the skeletal X-ray.
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Computed tomography (CT) scan
For a CT scan, you lie flat on a table while a machine rotates around your body and takes X-rays. A special dye may be injected into your veins and you may be asked to drink a special fluid in order to make the internal organs stand out. A CT scan may reveal the starting location of tumors and whether or not the cancer has spread to other parts of the body.
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Magnetic resonance imaging (MRI) scan
Magnetic resonance imaging (MRI) uses radio waves and a strong magnet to create clear and detailed images of body parts. Special waves are absorbed by the body and then released in a certain pattern, which is translated by a computer in order to show "slices" of the body. Doctors use MRIs to assess cancer spread and look at structures like the brain and spinal cord.
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Positron emission tomography (PET) scan
For a PET scan, the doctor injects a radioactive sugar into the patient's bloodstream. This substance collects in malignant (cancerous) cells in the patient's body. The doctor then uses a PET scanner to detect these areas of radioactivity and to find the exact location and level of metabolic activity of cancer in the patient's body.
Biopsy/Mutation testing
If any of these diagnostic tests indicate that you might have cancer, your doctor will conduct a biopsy to be certain. Your doctor will remove a tissue sample and have a pathologist examine it under a microscope to determine if it contains cancer cells. A biopsy is the only way to be certain of a cancer diagnosis. Your doctor will most likely take a biopsy sample while performing an endoscopy. If your doctor notices an abnormality during the procedure, he will pass a special tool through the endoscope and use it to take a tissue sample. Mutation testing on a GIST tumor sample helps identify specific genetic alterations (mutations) that are driving the cancer's growth and progression. This information is crucial for guiding treatment decisions, as certain drugs target specific GIST mutations. For example, mutations in the KIT or PDGFRA genes are common in GIST and are often treated with imatinib or other tyrosine kinase inhibitors (TKIs)
