What are neuroendocrine tumours (NETs)?

A neuroendocrine tumour (NET) is a tumour that develops from cells of the neuroendocrine system.

Cells that are similar to nerve cells make up the neuroendocrine system. They make chemical messengers called hormones. Hormones control how different organs in the body work.

Neuroendocrine cells are found throughout the body, in organs such as the stomach, bowel and lungs.

NETs can be non-cancerous (benign) or cancerous (malignant). This information is about malignant tumours. It is mainly about NETs that affect the digestive system.

Types of NETs

Some NETs make extra hormones and cause symptoms. These are called functioning tumours.

Tumours that do not make extra hormones are called non-functioning tumours.

NETs are grouped according to where the cancer started (the primary tumour). For example:

  • small bowel NETs
  • large bowel NETs
  • appendix NETs
  • pancreatic NETs
  • stomach (gastric) NETs
  • lung NETs.

Rarely, NETs occur in other areas, including the:

  • liver
  • gallbladder
  • bile ducts
  • kidneys
  • ovaries
  • testicles.

You may hear some NETs referred to as carcinoid tumours. These are usually tumours of the digestive system or lungs.

NETs often grow slowly. They can be difficult to diagnose, as they may not cause symptoms for a long time. It may be several years before symptoms appear and the tumour is diagnosed. But some NETs grow faster and are more likely to spread to surrounding tissues and parts of the body.

Symptoms of neuroendocrine tumours (NETs)

Symptoms will depend on where in the body the NET is. For example, a NET in the digestive system,  can cause pain in the tummy, sickness or diarrhoea. A NET in the lung may cause chest infections and shortness of breath.

Some NETS don't cause symptoms and are found by chance.

NETs sometimes make too much of certain hormones. The type of hormone they make depends on the gland the tumour is affecting.

If you are worried about NETs, we have more information about the signs and symptoms.

Causes of neuroendocrine tumours (NETs)

NETs are uncommon. We do not know what causes them.

These tumours can affect people of any age, but are most likely to develop in people over the age of 60. People with a rare condition called multiple endocrine neoplasia 1 (MEN1) have a higher risk of developing NETs.

Diagnosis of neuroendocrine tumours (NETs)

You usually start by seeing your GP. If they are unsure of the problem, they will refer you to a specialist at the hospital.

At the hospital, the doctor will ask about your general health and any previous medical problems. They will then examine you and talk to you about the tests you need to have.

Sometimes, NETs show up on a scan you may be having for another reason.

  • Urine and blood tests

    If you have a NET, the levels of some chemicals in the blood may rise. This is mainly serotonin and a protein called chromogranin A (CgA). You will need to give urine and blood samples to check the levels of these chemicals.

    You will also have a blood test to count the number of healthy blood cells in your blood. This is called a full blood count or FBC. Another blood test will check how well your kidneys and liver are working.

  • Ultrasound scan

    An ultrasound scan uses soundwaves to build up a picture of inside your body. Usually, you cannot eat or drink anything for at least 6 hours before the scan. You may also have an ultrasound of your heart, called an echocardiogram.

  • CT scan

    A CT scan uses x-rays to build a 3D picture of the inside of the body.

  • MRI scan

    An MRI scan uses magnetism to build up a detailed picture of areas of your body.

  • Nuclear medicine scans

    Nuclear medicine scans use a small amount of a radioactive substance called a tracer. The tracer shows up on scan pictures. The dose of radioactivity from these scans is low. It is about the same amount you get from an x-ray.

  • Biopsy

    During a biopsy, doctors take a small piece of tissue (or a sample of cells) from a tumour. They then look at it under a microscope. You have a local anaesthetic to numb the area before the sample is taken. Sometimes, you have a general anaesthetic for the biopsy. This depends on where the NET is in your body.

Waiting for test results can be a difficult time, we have more information that can help.

Further tests

Depending on the type of NET you have, your doctor may want to do other tests, including:

  • Bone scan
    A bone scan finds any abnormal areas of bone. A mildly radioactive substance is injected into a vein. A scan of your bones is taken 2 or 3 hours later.

  • Endoscopy
    An endoscopy uses a thin, flexible tube with a camera at the end to look inside the gullet, stomach, small bowel or large bowel.

Your doctor or nurse will explain the test to you and why you need it.

Staging and grading of neuroendocrine tumours (NETs)

The results of your tests help your doctors find out more about the size and position of the cancer and whether it has spread. This is called staging.

A doctor decides the grade of the cancer by how the cancer cells look under the microscope. This gives an idea of how quickly the cancer might grow or spread.

Knowing the stage and grade helps your doctors plan the best treatment for you.

Treatment for neuroendocrine tumours (NETs)

A team of specialists will meet to discuss the best possible treatment for you. This is called a multidisciplinary team (MDT).

They will discuss the results of your tests to plan your treatment. They will look at factors including:

  • where the NET started
  • the size of the tumour and whether it has spread (its stage)
  • whether you have symptoms of carcinoid syndrome or the over-production of other hormones
  • the appearance of the cells under a microscope (its grade).

Your doctor or cancer specialist or nurse will explain the different treatments and their side effects. They will also talk to you about things to think about when making treatment decisions.

The main treatment is surgery to remove the tumour. The aim of this is to cure the cancer. If surgery cannot completely remove the NET, treatment will aim to relieve symptoms and improve quality of life. 

Other treatment options you may have include:

  • Watchful waiting

    Some NETs are slow-growing and may not change for months or years. If a NET spreads but is not causing symptoms, you may not need treatment straight away. Your doctor will monitor you with regular check-ups. You will have the option of treatment if symptoms develop.

  • Somatostatin analogues

    Somatostatin analogues are drugs that treat the symptoms of carcinoid syndrome. They work by stopping the body making too many hormones. They may also control the growth of NETs. You may be given them along with other treatments.

  • Chemotherapy

    Chemotherapy uses anti-cancer (cytotoxic) drugs to destroy cancer cells. You may have chemotherapy to treat NETs that have spread. The type of chemotherapy you will have depends on where the NET started in the body.

  • Targeted therapies

    Targeted therapies are anti-cancer medicines that interfere with how cancer cells grow and divide. The two main targeted therapy drugs used are sunitinib (Sutent®) and everolimus (Afinitor®). You take these drugs as capsules or tablets.

  • Interferon alpha (IntronA®)

    Interferon is a drug that can treat the symptoms of NETs. It may also control how the tumour grows. Interferon is a protein that you naturally have small amounts of in your body. If you have it as a drug, it can stimulate the body’s immune system to destroy cancer cells. You will have it as an injection under the skin.

  • Radiotherapy

    Radiotherapy uses high-energy x-rays to destroy cancer cells, while doing as little harm as possible to normal cells. You may have radiotherapy if it is not possible to remove the tumour with surgery, or if it has already spread.

  • Targeted radionuclide therapy

    You may have radionuclide therapy to relieve symptoms of carcinoid syndrome and control the growth of NETs. This therapy uses a radioactive substance called a radionuclide. It is injected into the bloodstream.

Treatments for NETs in the liver

Treatments that directly target the liver can sometimes treat NETs in the liver:

  • Hepatic artery embolisation

    A hepatic artery embolisation can sometimes shrink NETs in the liver. It can also relieve the symptoms of carcinoid syndrome. Hepatic artery embolisation works by reducing blood flow to the tumours. Tumours need a blood supply to survive.

  • Radiofrequency ablation (RFA)

    Radiofrequency ablation (RFA) can treat NETs in the liver. It uses laser or radio waves to destroy the cancer cells by heating them to high temperatures. 

  • Selective internal radiation therapy (SIRT)

    Selective internal radiation therapy is a type of cancer treatment that uses tiny radioactive beads. It can treat secondary tumours (metastases) in the liver. 

Cancer research trials

Cancer doctors use cancer research trials to assess new treatments. Current studies are looking at new treatments for NETs.

Your doctor may ask you to take part in a cancer research trial. They will discuss the treatment with you, so you understand the trial and what it means to take part.

After neuroendocrine tumours (NETs) treatment

You have regular follow-up appointments after treatment.

After treatment, some people may be cured of NETs. Others may continue to have treatment when they need it to help keep it under control.  

If the cancer is advanced there are different things that can be done to control the symptoms. You can read more about this in our information on advanced cancer.

Well-being and recovery

Even if you already have a healthy lifestyle, you may choose to make some positive lifestyle changes after treatment.

Making small changes to the way you live such as eating well and keeping active can improve your health and well-being and help your body recover.

It can be difficult to eat well after treatment for head and neck cancer, but your dietitian can help you.

Your feelings after treatment

You may have many different emotions, including anxiety, anger and fear. These are all normal reactions. It may help to get support from family, friends or support organisations, like Neuroendocrine Cancer UK, who can give you information about counselling in your area.

Macmillan is also here to support you. If you would like to talk, you can:

About our information

  • Reviewers

    This information has been written, revised and edited by Macmillan Cancer Support’s Cancer Information Development team. It has been reviewed by expert medical and health professionals and people living with cancer. It has been approved by Chief Medical Editor, Professor Tim Iveson, Consultant Medical Oncologist.

    Our cancer information has been awarded the PIF TICK. Created by the Patient Information Forum, this quality mark shows we meet PIF’s 10 criteria for trustworthy health information.

Reviewed: 30 June 2018
Reviewed: 30/06/2018
Next review: 31 December 2020
Next review: 31/12/2020

This content is currently being reviewed. New information will be coming soon.