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What are carcinoid tumours?

Men and women discussing carcinoid cancer

Carcinoids are tumours of the neuroendocrine system. They are also called neuroendocrine tumours (NETs).

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What are carcinoid tumours?

Carcinoids are rare tumours which tend to be slow growing. They are a type of tumour of the neuroendocrine system. They are also called neuroendocrine tumours (NETs).

Carcinoids may not cause symptoms for several years. The average age of people diagnosed is around 60.

Most carcinoid tumours are found in the digestive system, but they can also develop in the lung, pancreas, kidney, ovaries or testicles. 

Carcinoid tumours and the neuroendocrine system

The neuroendocrine system is made up of nerve and gland cells. It makes hormones and then releases them into the bloodstream. There are neuroendocrine cells in many areas of the body, including the gut, lungs and pancreas. Carcinoids develop when changes happen to the neuroendocrine cells and they grow uncontrollably to form a tumour. Some carcinoid tumours can spread to other areas of the body, such as the liver.

What is carcinoid syndrome?

Some carcinoid tumours release hormones that cause particular symptoms, such as flushing of the skin, diarrhoea and wheezing. Doctors call this collection of symptoms carcinoid syndrome.

 

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How and where carcinoid tumours develop

Carcinoids are rare tumours which tend to be slow growing. They may not cause any symptoms for several years. They can develop at any age, but the average age of diagnosis is around 60.

Carcinoid tumours are a type of tumour of the neuroendocrine system. They are now classified as neuroendocrine tumours (NETs), but your doctor may still use the term carcinoid.

Around 70 out of 100 carcinoid tumours (70%) start in the digestive system. This is also called the gastrointestinal (GI) tract. It includes the food pipe (oesophagus), stomach, small bowel, appendix, large bowel (colon), and rectum. They are most often diagnosed in the small bowel.

Around 25 in 100 carcinoid tumours develop in the lung (25%). There are 2 types of lung carcinoid. Doctors can only tell the difference by looking at the cells under the microscope.

  • Typical lung carcinoids grow slowly and rarely spread to other parts of the body
  • Atypical lung carcinoids are much rarer, tend to grow faster and are slightly more likely to spread to other parts of the body than typical lung carcinoids

Carcinoids can also develop in the pancreas, kidney, ovary or testicle. In some cases doctors do not know where the original tumour developed.

Some carcinoid tumours can spread. The most common site of spread is to the liver, but they may also spread to lymph nodes or bone.

The diagram below shows the areas where carcinoid can develop.

Diagram showing the areas that might be affected by carcinoid

 

Carcinoid tumours and the neuroendocrine system

The neuroendocrine system is made up of nerve and gland cells. It makes hormones and then releases them into the bloodstream.

There are neuroendocrine cells in

  • The gut, including the food pipe (oesophagus)
  • The lungs
  • The pancreas

Neuroendocrine cells have different functions depending on where they are in the body. For example, the ones in the gut make hormones to control

  • The release of digestive juices into the gut
  • The muscles that move food through the bowel

And neuroendocrine cells in the lung release hormones that control the flow of air and blood in the lungs.

Carcinoids develop when changes happen in the neuroendocrine cells and they grow uncontrollably to form a tumour.

 

What carcinoid syndrome is

Some carcinoid tumours release hormones that cause particular symptoms. Doctors call this collection of symptoms carcinoid syndrome. It is more likely to happen if the carcinoid tumour has spread from its original place to other parts of the body, especially the liver.

The symptoms of carcinoid syndrome include

  • Flushing of the skin
  • Diarrhoea
  • Wheezing
  • A fast heart beat
  • Dizziness due to sudden low blood pressure

Drinking alcohol can bring on the symptoms in some people with carcinoid.

Find out more about the symptoms of carcinoid syndrome.

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Updated: 19 May 2016