A carcinoid tumour is a rare cancer of the neuroendocrine system – the body system that produces hormones.
The tumour usually grows in the bowels or appendix, but it can also be found in the stomach, pancreas, lung, breast, kidney, ovaries or testicles. It tends to grow very slowly.
"Carcinoid syndrome" is the collection of symptoms some people get when a carcinoid tumour – usually one that has spread to the liver – releases hormones such as serotonin into the bloodstream.
About 1,200 people are diagnosed with a carcinoid tumour each year in the UK, but it's thought that less than 1 in 10 of them will have carcinoid syndrome.
In the early stages of having a carcinoid tumour, you may not have any symptoms. You may also not have symptoms if the tumour is just in your digestive system, as any hormones it produces will be broken down by your liver.
If symptoms do develop, they tend to be fairly general and can be easily mistaken for signs of other illnesses.
Symptoms may result from both the tumour itself and from any hormones it releases into the bloodstream.
Symptoms will depend on where in the body the tumour develops:
Some tumours may not cause any symptoms and are discovered by chance. For example, an appendix carcinoid tumour may only be found when the appendix is being removed for another reason.
Typical symptoms of carcinoid syndrome include:
These symptoms may come on unexpectedly, as the hormones can be produced by the tumour at any time.
Some people may also develop carcinoid heart disease, where the heart valves thicken and stop working properly. There is also a risk of developing a rare but serious reaction called a carcinoid crisis, which involves severe flushing, breathlessness and a drop in blood pressure.
It's not known exactly why carcinoid tumours develop, but it's thought that most occur by chance.
Your chances of developing a carcinoid tumour may be increased if you have:
You can read more about the possible risk factors for carcinoid tumours on the Cancer Research UK website.
A carcinoid tumour may be found incidentally – for example, as a surgeon is removing an appendix. In this case, the tumour will often be caught early and removed along with the appendix, causing no further problems.
Otherwise, people usually see their GP after they have developed symptoms, and a carcinoid tumour may be diagnosed after carrying out a series of scans and tests, which may include measuring the amount of serotonin in your urine and having an endoscopy.
You can read more about the tests for carcinoid tumours on the Cancer Research UK website.
If the tumour is caught early, it may be possible to completely remove it and cure the cancer altogether. Otherwise, surgeons will remove as much of the tumour as possible (debulking).
You can read more about the surgery for carcinoid tumours on the Cancer Research UK website.
If the tumour cannot be removed, but it's not growing or causing symptoms, you may not need treatment straight away – it might just be carefully monitored.
If it's causing symptoms, you may be offered one of the following treatments:
Symptoms of carcinoid syndrome can be treated with injections of octreotide and lanreotide. You may also be given medication to widen your airways (to relieve wheezing and breathlessness) and anti-diarrhoea medication.
There are things you can do yourself to manage some of the symptoms of carcinoid syndrome.
Generally, you should avoid triggers of flushing, such as:
Some medications, such as selective serotonin reuptake inhibitor (SSRI) antidepressants, may make symptoms worse by further increasing your levels of serotonin – but never stop taking medication without seeking medical advice.
If you have diarrhoea, it's important to keep drinking little and often to avoid dehydration.
If the whole tumour can be removed, this may cure the cancer and symptoms altogether. But even if surgeons cannot remove the entire tumour, it usually grows slowly and can be controlled with medication.
Overall, people with carcinoid tumours have a good life expectancy compared to many other cancers, with around 70-80% surviving at least five years from diagnosis. Many people remain relatively well and lead active lives, with only occasional symptoms.
But as the tumour grows or spreads, it will produce more and more hormones, and it may eventually be difficult to completely control symptoms with medication. You may need further surgery or other treatments.
Unfortunately, life expectancy is not as good for cancer that has spread to other parts of your body, because it won't usually be possible to remove all of it. However, treatment can still control your symptoms and slow down the spread of cancer.
You can read more about the statistics and outlook for carcinoid on the Cancer Research UK website.
If you have carcinoid syndrome, your clinical team will pass information about you on to the National Congenital Anomaly and Rare Diseases Registration Service (NCARDRS).
This helps scientists look for better ways to prevent and treat this condition. You can opt out of the register at any time.