Neuroendocrine tumours (NETs) are a wide-ranging group of rare tumours that develop from neuroendocrine cells.

Neuroendocrine cells are specialised cells throughout the body that release chemicals called hormones into the blood when they are stimulated by nerves.

NETs may be malignant (cancerous) or benign (not cancerous) and are often slow-growing.

The most common NETs are: 

• Gastrointestinal NETs, including carcinoid tumours, which most commonly develop in the digestive system
• Lung NETs
• Pancreatic NETs, which develop in the pancreas and can affect the release of hormones

Pancreatic NETs can be either functioning or non-functioning. Functioning pancreatic NETs produce hormones that cause a specific group of symptoms (see below), depending on which cells are affected.

More rarely, NETs can develop in other parts of the body as well.

Symptoms of neuroendocrine tumours

The symptoms of a neuroendocrine tumour can vary depending on where it is and whether it affects the production of hormones.

Tumours that do not cause any specific noticeable symptoms are referred to as non-functioning tumours.

Sometimes, the symptoms can be quite vague. For example, a tumour in the digestive system may cause diarrhoea, constipation and tummy pains, or a tumour in the lung may cause wheezing or a persistent cough.

Tumours that affect hormone production are described as functioning tumours and may cause abnormally large amounts of hormones to be released into the blood. This can cause noticeable symptoms such as flushing, cramps, wheezing, low blood sugar, blood pressure changes, and heart problems.

What causes neuroendocrine tumours?

It is not yet fully understood what causes neuroendocrine tumours.

However, some neuroendocrine tumours, such as multiple endocrine neoplasia (MEN 1), are genetic and therefore there is an increased risk if another member of your direct family, such as a parent, has this type of neuroendocrine tumour.

Diagnosis

There are many tests that can be used to diagnose NETs, including blood tests, urine tests, and a biopsy.

Different types of scans may also be used to look for, or examine, tumours. These include:

• ultrasound scans, including echocardiograms and endoscopic ultrasound scans
• computerised tomography (CT) scans
• magnetic resonance imaging (MRI) scans
• positron emission tomography (PET) scans
• octreotide scans, where a mildly radioactive liquid is injected into your veins so any cancerous cells are highlighted when studied with a special camera

Treating neuroendocrine tumours

Treatment for neuroendocrine tumours is highly individual to you, as it depends on where your tumour is, how advanced your condition is and your general health.

If the tumour is benign, or has not spread to other parts of your body, it may be surgically removed.

Unfortunately, many patients are only diagnosed after other parts of the body are affected, when surgery is very difficult.

If surgery cannot be used to cure you, then it may be used to help manage your condition and reduce any symptoms. Treatments such as somatostatin analogues, peptide receptor targeted therapy (PRRT), embolisation, interferon, chemotherapy, radiotherapy, radiofrequency ablation (which uses heat to destroy cells), sunitinib or everolimus may be also used to stabilise the tumours.

Want to know more?

• Cancer
• NET Patient Foundation
• Macmillan – Neuroendocrine tumours
• Cancer research UK – What are neuroendocrine tumours?