To diagnose a gastrointestinal stromal tumor, your healthcare professional might start by asking you about your symptoms and your health. This cancer, which also is called a GIST, happens in the digestive system.

If symptoms suggest that you may have a GIST, you might need other tests to find the cancer. These tests may include:

• Imaging tests. Imaging tests help your healthcare team find your tumor and see its size. Tests might include ultrasound, CT, MRI and positron emission tomography (PET) scans. Not everyone needs every test.
• Upper endoscopy. This test uses a long, thin tube (endoscope) with a light on the end. The tube goes through the mouth and down the throat. This test looks at the inside of the esophagus, stomach and the first part of the small intestine.
• Endoscopic ultrasound (EUS). This test also uses an endoscope, but with an ultrasound probe on the tip of the scope. The ultrasound probe uses sound waves to make pictures of the tumor and show its size.

• Fine-needle aspiration biopsy. This test collects a small sample of tissue from the tumor so it can be tested in a lab. This test is like EUS, but with a thin, hollow needle on the tip of the endoscope. The EUS finds the tumor. The needle collects small amounts of tissue for the lab tests.

  Sometimes the needle can't get enough cells, or the results aren't clear. You might need surgery to collect the sample.

• Laboratory tests on biopsies. The biopsy sample from your tumor goes to a lab for testing. In the lab, specialists test the cells to see if they're cancer cells. Other tests give your healthcare professional details about your cancer cells that are used to plan your treatment.