Diagnosis

Doctors use many tests to diagnose a tumor and determine if it has metastasized (spread). Some tests may also determine which treatments may be the most effective. For most types of tumors, a biopsy is the only way to make a definitive diagnosis of cancer. If a biopsy is not possible, the doctor may suggest other tests that will help make a diagnosis. Imaging tests may be used to find out whether the cancer has metastasized. Your doctor may consider these factors when choosing a diagnostic test:

• Age and medical condition
  
  
• The type of tumor suspected
  
  
• Severity of symptoms
  
  
• Previous test results

In addition to a physical examination, the following tests may be used to diagnose GIST:

Blood/urine tests. Several laboratory tests may be conducted, including a blood test to check several organ functions and a urine test to detect protein, sugar, or other abnormalities.

Computed tomography (CT or CAT) scan. A CT scan creates a three-dimensional picture of the inside of the body with an x-ray machine. A computer then combines these images into a detailed, cross-sectional view that shows any abnormalities or tumors. Sometimes, a contrast medium (a special dye) is injected into a vein to provide better detail. For patients with GIST, the CT scan is the most commonly used diagnostic tool. A CT scan can help doctors determine whether the cancer has spread to the liver.

Fecal occult blood test. This test detects occult (hidden) blood in the stool, which can be caused by cancer in the GI tract. A small amount of stool is placed on a plastic slide or special paper and is tested in the doctor's office or a laboratory.

X-ray. An x-ray is a picture of the inside of the body. For instance, a chest x-ray can help doctors determine if the cancer has spread to the lungs. X-rays may be taken of the esophagus and stomach, which are referred to as the upper GI tract. This procedure is also called a barium swallow, because the x-rays are taken after a patient drinks a substance called barium, which outlines the GI tract on the x-ray and helps the doctor see a tumor or other abnormal areas. In a barium enema, the doctor looks at the lining of the colon and rectum on the x-ray after the barium is administered through the anus.

Endoscopy. This test allows the doctor to see the inside of the stomach. The patient may be sedated, and the doctor inserts a thin, lighted tube called a gastroscope through the mouth, down the esophagus, and into the stomach and small bowel. If abnormal areas are found, the doctor can remove a sample of tissue and check it for evidence of cancer.

Endoscopic ultrasound. This test is similar to an endoscopy, but the gastroscope has a small ultrasound probe on the end that uses sound waves to create an image of the stomach. The ultrasound image helps doctors determine if or how far the cancer has spread into the stomach and nearby tissues.

Magnetic resonance imaging (MRI). An MRI uses magnetic fields, not x-rays, to produce detailed images of the body. A contrast medium may be injected into a patient’s vein to create a clearer picture.

Positron emission tomography (PET) scan. A PET scan is a way to create pictures of organs and tissues inside the body. A small amount of a radioactive substance is injected into a patient’s body and absorbed by the organs or tissues being studied. PET scans are often used to complement information gathered from CT scan, MRI, and physical examination, and may be used to document early growth of the disease (called PET flare), or to measure the tumor’s early response to treatment.

Biopsy. It is vitally important to be seen by a team of medical and surgical oncologists experienced in the treatment of GIST before any surgery or biopsy are performed. A biopsy is the removal of a small amount of tissue for examination under a microscope. Other tests can suggest that cancer is present, but only a biopsy can make a definite diagnosis. The sample removed from the biopsy is analyzed by a pathologist (a doctor who specializes in interpreting laboratory tests and evaluating cells, tissues, and organs to diagnose disease). The type of biopsy performed will depend on the location of the cancer. In the case of GIST, the patient may still be monitored even if the biopsy results do not indicate cancer, as a biopsy for GIST is not always definitive.

To learn more about what to expect during common diagnostic tests, read Cancer.Net: Tests and Procedures.

To learn about the terms used in this section, read the Cancer.Net Feature: Cancer Terms to Know: Newly Diagnosed.