This website is intended for an international audience, excluding the UK, United States, Canada and France
This website is intended for an international audience, excluding the UK, United States, Canada and France

NETs: key facts

Dr Geboes defines NETs


The healthcare professional shown in this video speaks about their own opinions and experiences and not about any specific patient. Some treatment options may not be authorized or available in your country. Each person’s case is unique and you should always consult a doctor for information and advice about the diagnosis and treatment of NET. No information within this video constitutes medical advice.

The neuroendocrine system, also known as the hormone system, is made up of nerve and gland cells called neuroendocrine cells. These cells release hormones into your body that generally regulate the function of different organs.

When neuroendocrine cells change and grow uncontrollably, NETs can develop.NETs are cancerous but vary in their behaviour. Some NETs are towards the benign end of the spectrum and some towards the more aggressive or malignant end of the spectrum.

When NETs that grow slowly are confined to a limited area of the body (i.e. a low or intermediate grade) may generally be considered non-life threatening if they do not squeeze or replace other nearby areas of the body.

If feasible, NETs should be removed by surgery or otherwise treated in their early stages of development as they may spread to other sites of the body. The choice of treatment a person with NETs may receive is carefully adapted to each particular case and is the decision of a multidisciplinary care team.

Some NETs grow faster or more uncontrollably than others, perhaps affecting the surrounding tissues or moving from one area of the body to another (metastasised).

If surgery is not possible there are still treatment options for people with metastatic NETs.


Functioning vs non-functioning tumours

You may hear NETs referred to as being functioning or non-functioning. Some NETs produce too many hormones that can cause various symptoms and complications, depending upon the tumour’s location and the hormones that it releases.

These NETs are called functioning tumours. NETs that don’t produce hormones are called non-functioning tumours, although they can still cause complications.

What are carcinoid tumours and carcinoid syndrome?

Carcinoid tumours and carcinoid syndrome are two different conditions.

Many people still refer to NETs as carcinoid tumours. This is an older term that is sometimes still used as an alternative for either NETs in general, or NETs that do not originate in the pancreas.

In 1907, NETs were first named carcinoid tumours because scientists thought their slow growth meant they were ‘cancer-like’ (benign) tumours rather than truly cancerous (malignant).

It is now clear that that NETs can be malignant and spread from one part of the body to another, like other forms of cancer.

Carcinoid syndrome, on the other hand, is a distinct group of symptoms that some people with neuroendocrine tumours (NETs) may get when NETS from the small intestine (and sometimes other sites) spread to other parts of the body, usually the liver.

The main symptoms of carcinoid syndrome include diarrhoea, flushing of the skin (particularly the face) and stomach cramping, but can include heart problems such as palpitations, and wheezing.

Carcinoid syndrome affects approximately 20% of patients with NETs at diagnosis and is caused by hormones being over produced by tumour cells.


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This website is intended for an international audience, excluding the UK, United States, Canada and France. This website has been developed by Ipsen in collaboration with those living with NETs and the healthcare professionals who care for them. Ipsen would like to thank everyone for their valuable insights and stories. All names used on this website are not necessarily real names. Visit for more information about us. Website design and development by Kanga Health Ltd. ALL-ALL-002300/November 2020