Neuroendocrine tumors (NETs) are either benign or cancerous tumors that grow on a type of cell in the nervous system called neuroendocrine cells. These cells act like nerve cells but also produce hormones.

A tumor is a growth that develops when damage to a cell’s DNA causes it to copy itself excessively, forming a mass. Neuroendocrine tumors (NETs) can be either malignant, meaning they can grow and spread to other tissue, or benign, meaning they can grow but not spread.

This article discusses the types of NETs, symptoms, causes, treatment options, and more.

A person undergoing a CAT scan to diagnose neuroendocrine tumors -2.Share on Pinterest
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There are several types of NET that doctors define according to where they develop in the body. These include:

  • Gastroenteropancreatic NETs (GEP NETs): GEP NETs develop in the pancreas or gut. They include gastrointestinal NETs (GI NETs) that grow in the stomach, bowel, or food pipe.
  • Pulmonary NETs: These develop in the lungs. Pulmonary NETs are a rare type of lung cancer.
  • NETs in other organs: In rare cases, NETs may develop in other parts of the body, such as the:
    • liver
    • gallbladder
    • bile duct
    • kidneys
    • ovaries
    • testicles

Classifications of neuroendocrine tumor

Doctors classify NETs as either functional or nonfunctional.

Functional NETs produce hormones. Nonfunctional NETs do not produce a biologically active hormone, and these are the most common type.

Learn more about tumors.

NETs can cause general cancer symptoms, such as:

However, other symptoms may develop depending on which organ or tissue the tumor affects. Some symptoms depend on the location of the tumor, while others occur due to the hormones that an NET can release.

Symptoms due to tumor location

These might include:

  • GI NET symptoms: An NET in the digestive system can cause constipation, diarrhea, or stomach pain.
  • Pulmonary NET symptoms: Lung NETs can cause wheezing or constant coughing.
  • Other location-specific NET symptoms: Constant pain, thickening, or lumps in certain areas of the body may suggest a NET. Other symptoms can include:
    • changes in bladder or bowel habits
    • yellowing skin or eyes — jaundice
    • unusual bleeding and discharge

Symptoms due to excess hormone production

In functional NETs, the tumors may make too many hormones. This can cause symptoms, including:

Research into the direct causes of NETs is ongoing.

However, according to the U.K.’s National Health Service, people with several underlying health issues may have a higher risk of developing a NET. These include the following:

  • Multiple endocrine neoplasia type 1 (MEN 1): This is an inherited condition, meaning that it passes from parents to children in the genes. It causes tumors to develop in the hormone-producing system of the body, including the pancreas, parathyroid glands, and pituitary glands.
  • Neurofibromatosis type 1: This covers several genetic conditions that lead to tumor development on the nerves.
  • Von Hippel-Lindau syndrome (VHL): This inherited condition causes irregular growth in blood vessels.

NETs are difficult to diagnose. According to a 2016 study, people with NETs experience an average of 52 months between the start of symptoms and diagnosis. By the time many people receive a diagnosis, the NET may have spread to other tissues.

To assist with reaching an accurate diagnosis, a physician will typically need to collect tissue from the tumor and send it to a lab for analysis. Often, this will involve removing part or all of the tumor. However, when this is not possible, the physician may perform a core needle biopsy, in which they collect a smaller sample of tissue through a needle.

A person may also require an imaging test, such as a CT scan, to check for other NETs. They may scan the following areas:

  • chest
  • abdomen
  • pelvis
  • liver
  • pancreas

Doctors may also perform functional imaging. This shows excess hormone production in those with functional NETs by infusing an intravenous (IV), slightly radioactive dye that shows somatostatin receptors.

These receptors have links to hormone overproduction in NETs. The radiation appears on a scanner for the diagnostic team to track the tumor.

The type of treatment a doctor may recommend for someone with a NET depends on several factors, including:

  • the location of the tumor
  • the stage of the condition
  • the person’s overall health


The best treatment for a NET is surgery.

If a tumor has not spread from its original site, a surgeon may remove part or all of it. This can help treat the tumor and prevent it from spreading.


Some medications destroy cancer cells throughout the body, while others target local areas. An oncologist — a doctor specializing in cancer medications — may prescribe different types of medication treatments depending on the NET, including:

  • chemotherapy, which directly targets and kills cancer cells
  • immunotherapy, which uses a person’s own immune system to attack cancer cells
  • somatostatin analogs to control the symptoms of excess hormones from an NET
  • targeted therapy, which targets tumors through their unique genes

A person’s doctor can help create a suitable treatment plan.

NETs are rare, developing in 4 in every 100,000 adults. It is rare in children.

As the exact cause of NETs is unclear, prevention may not be possible. However, early identification of the tumor may improve an individual’s outlook. Therefore, it is best for a person to contact a doctor as soon as they have concerns.

Here are some common questions about neuroendocrine tumors (NETs).

Is a neuroendocrine tumor considered cancer?

NETs can be either cancerous or benign.

What is the survival rate for neuroendocrine tumors?

A 2018 study found significant differences in the survival rate among people with NETs. This may be because there are several types, classifications, and locations of NET.

A doctor can provide a clearer picture of a person’s outlook based on their individual circumstances.

Neuroendocrine tumors (NETs) develop on nerves on hormone-producing cells in the nervous system. They may develop in the gut, lungs, and pancreas, as well as in other locations. Sometimes, they produce excessive hormones that have effects throughout the body. Symptoms will depend on the location of the NET.

Some genetic and inherited conditions have links to NETs, but the exact cause of this is currently unclear.

A doctor may diagnose a NET through scans and biopsies. Surgery is the main treatment, though doctors may sometimes recommend medical treatments, such as chemotherapy, immunotherapy, and targeted therapy.