Neuroendocrine Tumor of the Gastrointestinal Tract: Diagnosis

Approved by the Cancer.Net Editorial Board, 08/2018

ON THIS PAGE: You will find a list of common tests, procedures, and scans that doctors use to find the cause of the medical problem. Use the menu to see other pages.

Doctors use many tests to find, or diagnose, a GI tract NET. They also do tests to learn if cancer has spread to another part of the body from where it started. If this happens, it is called metastasis. For example, imaging tests can show if the cancer has spread. Imaging tests show pictures of the inside of the body. Doctors may also do tests to learn which treatments could work best.

For most types of cancer, a biopsy is the only sure way for the doctor to know if an area of the body has a tumor. In a biopsy, the doctor takes a small sample of tissue for testing in a laboratory. If a biopsy is not possible, the doctor may suggest other tests that will help make a diagnosis.

This list describes options for diagnosing a GI tract NET. Not all tests listed below will be used for every person. Your doctor may consider these factors when choosing a diagnostic test:

  • The type of cancer suspected

  • Your signs and symptoms

  • Your age and general health

  • The results of earlier medical tests

Most GI tract NETs are found unexpectedly when people have x-rays or a medical procedure done for reasons unrelated to the tumor. For example, many NETs of the appendix are found during surgery to remove the appendix, called an appendectomy. NETs in the stomach and duodenum, the top of the small intestine, are usually found during an endoscopy (see below).

If a doctor suspects a GI tract NET, he or she will ask for a complete medical and family history and perform a thorough physical examination. In addition, the following tests may be used to diagnose a GI tract NET:

  • Blood/urine tests. The doctor may need samples of your blood and urine to check for abnormal levels of hormones and other substances. Urine tests check the amount of 5-HIAA, a product of serotonin breakdown. Serotonin, a neurotransmitter involved in behavior and depression, is made by some NETs. Measurements of serotonin levels may also be taken. A doctor may be able to diagnose a NET from a urine test alone. A blood test to measure chromogranin-A, a protein produced by tumor cells, may be needed since the serum serotonin level often changes and may not be as useful as a chromogranin-A test.

  • Biopsy. biopsy is the removal of a small amount of tissue for examination under a microscope. A pathologist then analyzes the sample(s) removed during the biopsy. A pathologist is a doctor who specializes in interpreting laboratory tests and evaluating cells, tissues, and organs to diagnose disease.

  • Molecular testing of the tumor. Your doctor may recommend running laboratory tests on a tumor sample to identify specific genes, proteins, and other factors unique to the tumor. Results of these tests will help decide whether your treatment options include a type of treatment called targeted therapy (see Types of Treatments).

  • Endoscopy. An endoscopy allows the doctor to see the lining of the upper digestive system with a thin, lighted, flexible tube called an endoscope. The person may be sedated as the tube is inserted through the mouth, down the esophagus, and into the stomach and small bowel. Sedation is giving medication to become more relaxed, calm, or sleepy. If an abnormality is found, a biopsy will be performed.

    colonoscope is a type of endoscope that is inserted through the anus and into the colon. It can be used to diagnose a tumor in the lower section of the digestive tract.

  • Endoscopic ultrasound. An ultrasound uses sound waves to create a picture of internal organs. This procedure is often done at the same time as an upper endoscopy. During an endoscopic ultrasound, a machine that produces the sound waves, called a transducer, is inserted into the upper digestive tract through the mouth. The endoscopic ultrasound can show enlarged lymph nodes, which may help the doctor find a tumor or figure out the stage of the disease.

  • X-ray. An x-ray is a way to create a picture of the structures inside the body. Sometimes, a GI tract NET may not show up on an x-ray because of its size or location so the doctor may also recommend other types of scans.

  • Barium x-rays. During a barium swallow, a person swallows a liquid containing barium that coats the lining of the esophagus, stomach, and intestines. Then a series of x-rays are taken. The barium makes abnormalities easier to see on the x-ray. If there is an abnormality, an endoscopic biopsy can help make a diagnosis of cancer.

    A barium enema may be given before x-rays are taken to show the inner surface of the large intestine. During this test, a barium solution is given through the anus and flows throughout the colon. Then the x-rays are taken.

  • Computed tomography (CT or CAT) scan. A CT scan takes pictures of the inside of the body using x-rays taken from different angles. A computer combines these images into a detailed, 3-dimensional image that shows any abnormalities or tumors. A CT scan can be used to measure the tumor’s size. Additionally, a CT scan is used to see if a tumor has spread to the liver and to find a NET in the retroperitoneal (the area behind the abdomen) lymph nodes. Sometimes, a special dye called a contrast medium is given before the scan to provide better detail on the image. This dye can be injected into a patient’s vein or given as a pill or liquid to swallow.

  • Magnetic resonance imaging (MRI). An MRI uses magnetic fields, not x-rays, to produce detailed images of the body. MRI can be used to measure the tumor’s size. A special dye called a contrast medium is given before the scan to create a clearer picture. This dye can be injected into a patient’s vein or given as a pill or liquid to swallow.

  • Nuclear medicine imaging. During this test, a small amount of a radioactive drug, called a tracer, is injected into a patient’s vein. The body is then scanned to show where the radioactivity has built up in the body. There are a few available methods of nuclear medicine imaging in NETs, including OctreoScan and 2 types of PET-CT scans.

    • OctreoScan. This imaging test uses octreotide linked with indium-111 as the tracer. This procedure is useful for identifying where a NET has spread, especially if it has spread to the liver. OctreoScan is slowly being replaced by the newer and more sensitive gallium-68 DOTATATE PET scan (see below).

    • Positron emission tomography (PET) or PET-CT scan.  A PET scan is usually combined with a CT scan (see above), called a PET or PET-CT scan. The 2 types of tracers used in a PET scan include gallium-68 (68Ga) DOTATATE and (18F) fluorodeoxyglucose (FDG). The 68Ga DOTATATE PET is the primary scan used to look at slow-growing NETs (grades 1 and 2, see Stages and Grades). An FDG PET scan is sometimes used for faster-growing NETs (grade 3).

After diagnostic tests are done, your doctor will review all of the results with you. If the diagnosis is cancer, these results also help the doctor describe the tumor. This is called staging.

The next section in this guide is Stages and Grades. It explains the system doctors use to describe the extent of the disease. Use the menu to choose a different section to read in this guide.