Diagnosing neuroendocrine tumors

This page was reviewed under our medical and editorial policy by

Maurie Markman, MD, President, Medicine & Science.

This page was updated on June 6, 2022.

There are many types of neuroendocrine tumors (NETs), and each requires a different approach to diagnosis and treatment. When diagnosing neuroendocrine tumors, multiple factors are considered, including the tumor’s type, where it’s located in the body, whether it’s producing excess hormones, whether it’s aggressive and how aggressive it is, and whether it’s spread (metastasized) to other parts of the body.

Neuroendocrine tumors may develop in different areas of the body—wherever there are hormone-making endocrine cells. Most tend to develop in the lungs, pancreas or gastrointestinal tract. Often, neuroendocrine tumors are found coincidentally during a procedure or imaging test happening for another reason. Neuroendocrine tumors of the appendix, for example, are often found during removal of the appendix to treat appendicitis. You may not have any symptoms related to a neuroendocrine tumor.

If your care team sees signs of a neuroendocrine tumor, a biopsy (a sampling of the tumor tissue) is the only way to tell for sure whether it’s cancer. However, you’ll probably need additional tests so your care team can determine the details—exactly where the tumor is, how big it is or other characteristics about the tumor—that may help in crafting your treatment plan.

Diagnosing a neuroendocrine tumor looks different for everyone. The tests your care team orders may depend on:

  • Suspected type of tumor
  • Symptoms
  • Age
  • General health

Because of this, if your care team finds something they suspect is cancerous, they may start by conducting a physical examination and reviewing your health history.

Our cancer experts use a variety of tools designed for diagnosing neuroendocrine tumors, evaluating the disease and planning your individualized treatment. The diagnostic tests we may use to diagnose NETs include:

  • Laboratory tests: Your care team may take a blood sample to check the levels of hormones—which are affected by neuroendocrine tumors—and other substances. They also may look for tumor markers, which are proteins that can provide information about tumor cells. For neuroendocrine tumors, a specific tumor marker called chromogranin A may be measured as part of your diagnosis.
  • Endoscopic ultrasound: Ultrasounds use sound waves to create images of areas in your body. Often, these sound waves are produced outside the body, on your skin. However, in order to see internal organs and lymph nodes more clearly, they’re sometimes produced from within via an endoscope. An endoscope is a long, thin tube with a camera and light attached. To diagnose neuroendocrine tumors of the pancreas or gastrointestinal tract, the endoscope is inserted through the mouth, windpipe and esophagus to get views of the pancreas and upper digestive tract. When an endoscope is used to inspect the lungs and lymph nodes to diagnose neuroendocrine tumors of the lung, it’s called an endobronchial ultrasound.
  • Endoscopic retrograde cholangiopancreatography (ERCP): This procedure combines an endoscopy and X-rays to get clear images of any areas of suspected cancer, especially in the ducts within the pancreas and liver. A contrast dye is used to produce clearer images. Because the procedure involves endoscopy, your care team may remove tissue during the procedure if necessary.
  • Biopsy: A sample of the suspected tumor tissue is removed for inspection in a lab. A pathologist will look at the sample under a microscope to determine whether it’s cancerous. There are several ways to get the tissue sample, including an endoscopic ultrasound or a laparoscopy, depending on where the suspected tumor is located.
  • Cytopathology: Less invasive than a tissue biopsy, cytopathology tests may be used to examine small samples of fluid or cells to check for signs of cancer. Your care team may get a sample of cells using a thin needle or by brushing or scraping cells off of tissue. A well-known cytopathology test is the Pap test to screen for cervical cancer.
  • Computed tomography (CT): These scans use X-rays to produce 3D images of an area of your body. They’re especially helpful in viewing lymph nodes or other organs, such as the liver, that may be affected by a nearby neuroendocrine tumor. They may also be used to tell the size of a tumor. When a CT scan is done using contrast dye—either given by injection or as a pill to swallow—it’s called a CT angiography.
  • Magnetic resonance imaging (MRI): This test produces images of your body using magnetic fields, not radiation. An MRI may be used to tell how large a tumor is or to scan an area of your body where cancer may have spread. Pancreatic neuroendocrine tumors and their metastases (spread) are sometimes seen most clearly via MRIs. Before the MRI begins, you may receive a contrast dye—either by injection or swallowed as a pill—that helps the images show up clearly.
  • Laparoscopy: A minimally invasive surgery, a laparoscopy uses a thin tube with a light and a camera to examine areas inside your abdomen. One or several small incisions may be made, and if your care team finds any tissue they suspect is cancerous and want a sample, they may remove some for testing (biopsy) during the laparoscopy.
  • Nuclear medicine imaging: There are several types of nuclear medicine imaging tests, and all of them use a medicine with low-level radiation as a tracer to find fast-growing cells in your body. This medicine is typically given by injection, but it may also be given as a pill or inhaled as a gas. In nuclear scans for cancer, the tracer makes its way through your body, accumulating in fast-growing cells that often signal cancer. Nuclear medicine imaging may be done using a positron emission tomography (PET) scan or a combination of a PET scan and CT scan (PET-CT).
  • Genetic testing and counseling: Testing the tumor cells for specific genes in order to identify targeted treatment options may be an option, but it’s generally less helpful for neuroendocrine tumors than other types of cancer.

Some of these tests are quick and simple, while others are more invasive and time-consuming. For some of these procedures, you may be sedated in order to be most comfortable. For any test that your care team recommends, be sure to ask your questions so you feel better prepared.

What’s next?

Your care team may review your test results with you, likely using several test results to put together a comprehensive picture of the neuroendocrine tumor and any metastases. These test results help lay the foundation for the treatment options you and your care team may discuss.

Along with the test results, your treatment options may also be informed by your overall health, personal preferences, age and any other known health conditions.

As you process the information from your test results, you may have a lot of questions. Consider asking the following questions:

  • May I get a copy of each of my test results?
  • Do I need further tests at this time?
  • When will we know the stage of the cancer?
  • Where did the cancer start?
  • Has the cancer spread to other sites?
  • When can we discuss treatment options?

Next topic: How are neuroendocrine tumors treated?

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