Neuroendocrine Tumor: Diagnosis

Approved by the Cancer.Net Editorial Board, 11/2016

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

Doctors use many tests to find, or diagnose, a tumor. They also do tests to learn if the tumor is cancerous, and if so, if it 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 tumor 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 tumors, a biopsy is the only sure way for the doctor to know whether an area of the body has cancer. 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 this type of tumor. 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 tumor suspected

  • Your signs and symptoms

  • Your age and medical condition

  • The results of earlier medical tests

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

  • Blood/urine tests. The doctor may collect blood and urine samples to check for abnormal levels of hormones and other substances. Urine tests check for increased levels of adrenaline in the body. Large amounts of adrenaline can be a sign of pheochromocytoma.

    The glucagon stimulation test and clonidine (Catapres) suppression test are blood tests that measure adrenaline levels for people who sometimes have symptoms of pheochromocytoma. During the glucagon stimulation test, glucagon is injected into a vein. Glucagon is a hormone produced by the pancreas that helps the body process carbohydrates. Blood samples are then drawn at specific times to measure adrenaline levels.

    During the clonidine suppression test, a tablet of the drug clonidine is swallowed, and blood samples are taken at regular intervals over the next 3 hours. Clonidine is used to lower adrenaline levels in the blood, so if these levels do not decrease during testing, it may be a sign of a tumor. Blood pressure and heart rate are also carefully monitored during these tests.

  • X-ray. An x-ray is a way to create a picture of the structures inside of the body, using a small amount of radiation.

  • Computed tomography (CT or CAT) scan. A CT scan creates a 3-dimensional picture of the inside of the body using x-rays taken from different angles. A computer then combines these images into a detailed, cross-sectional view that shows any abnormalities or tumor. A CT scan can also be used to measure a tumor’s size. 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 liquid to swallow.

  • Magnetic resonance imaging (MRI). An MRI uses magnetic fields, not x-rays, to produce detailed images of the body. MRI can also be used to measure a 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 liquid to swallow.

  • Biopsy. A 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. Other tests can suggest that a tumor is present, but only a biopsy can make a definite diagnosis.

  • 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 the Treatment Options section for more information.

  • Positron emission tomography (PET) or PET-CT scan. A PET scan is usually combined with a CT scan, called a PET-CT scan. However, you may hear your doctor refer to this procedure just as a PET scan. A PET scan is a way to create pictures of organs and tissues inside the body. A small amount of a radioactive sugar substance is injected into the patient’s body. This sugar substance is taken up by cells that use the most energy. Because cancer tends to use energy actively, it absorbs more of the radioactive substance. A scanner then detects this substance to produce images of the inside of the body. Some centers are researching the role of PET or PET-CT scans regarding Merkel cell cancer, for both staging and ongoing monitoring of patients during treatment.

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

The next section in this guide is Stages. It explains the system doctors use to describe the extent of a cancerous neuroendocrine tumor. Or, use the menu to choose another section to continue reading this guide.