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. Diagnosing neuroendocrine tumors involves multiple factors, including the tumor’s type, where it’s located in the body, whether it’s producing excess hormones, 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 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. Patients may not have any symptoms related to a neuroendocrine tumor.

If the 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, patients will probably need additional tests so the 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 the treatment plan.

Tests for neuroendocrine cancer diagnosis

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

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

If the care team finds something they suspect is cancerous, they may start by conducting a physical examination and reviewing the patient's health history.

Cancer experts use a variety of tools to diagnose neuroendocrine tumors, evaluate the disease and plan for an individualized treatment strategy. 

Laboratory tests

Laboratory tests help the care team in determining a neuroendocrine tumor diagnosis. For instance, the 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 the diagnostic process.

Imaging tests

The care team may order a variety of imaging tests and scans, including those listed below, during the NET diagnosis process.

Endoscopic ultrasound: Ultrasounds use sound waves to create images of areas in the body. Often, these sound waves are produced outside the body, on the 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, the 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 examines the sample under a microscope to determine whether it’s cancerous. Tissue samples may be extracted using various techniques, 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. The care team may get a sample of cells using a thin needle or by brushing or scraping cells off tissue. One 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 the 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 performed 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 the body using magnetic fields, not radiation. An MRI may be used to tell how large a tumor is or to scan an area of the body where cancer may have spread. Pancreatic neuroendocrine tumors and their metastases (cancer cells that have spread) are sometimes seen most clearly via MRIs. Before the MRI begins, the patient 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 attached to examine areas inside the abdomen. One or several small incisions may be made, and if the 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 that use a medicine with low-level radiation as a tracer to find fast-growing cells in the 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 the 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 tumor cells for specific genes may help in identifying a targeted treatment option. But genetic testing and counseling are 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, the patient may be sedated in order to be most comfortable. For any test the care team recommends, be sure to ask questions to better prepare.

Evaluating NET cancer test results

The care team may review the patient's test results with him or her, likely using several test results to put together a comprehensive picture of the neuroendocrine tumor and any metastases (or cancer spread). These test results help lay the foundation for the treatment options the patient and his or her care team may discuss.

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

As patients process the information from the test results, it's normal to have a lot of questions. Among them:

  • 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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