A neuroendocrine tumour is a rare tumour that can develop in many different organs of the body. It affects the cells that release hormones into the bloodstream (neuroendocrine cells).

Neuroendocrine tumours can be cancerous (malignant) or non-cancerous (benign). They often grow slowly, but not always.

Symptoms of neuroendocrine tumours

The symptoms of a neuroendocrine tumour depend on where in the body it is and what hormones it produces.

For example, a tumour in the digestive system (gastrointestinal neuroendocrine tumour) may cause diarrhoea, constipation or tummy pains.

A tumour in the lung (pulmonary neuroendocrine tumour) may cause wheezing or a persistent cough.

Some tumours may lead to abnormally large amounts of hormones being released into the bloodstream. These are known as "functioning tumours" and can cause symptoms such as diarrhoea, flushing, cramps, wheezing, low blood sugar (hypoglycaemia), changes in blood pressure and heart problems.

Causes of neuroendocrine tumours

The cause of neuroendocrine tumours isn't fully understood. However, your chance of developing one is increased if you have one of the following inherited conditions:

• multiple endocrine neoplasia type 1 (MEN1)
• neurofibromatosis type 1
• Von Hippel-Lindau syndrome (VHL)

Research suggests your risk of developing a neuroendocrine tumour is slightly increased if your father, mother, brother or sister has had any type of cancer.

Diagnosing neuroendocrine tumours

Many tests can be used to diagnose neuroendocrine tumours, including blood tests, urine tests, scans and a biopsy (where a small tissue sample is taken for closer examination).

Types of scans used include:

• ultrasound
• CT (computerised tomography)
• MRI (magnetic resonance imaging)
• PET (positron emission tomography)
• octreotide scans – where mildly radioactive liquid is injected into your veins and a special camera is used to highlight any cancerous cells

Treatment for neuroendocrine tumours

How a neuroendocrine tumour is treated will depend on your individual circumstances, such as:

• where the tumour is
• how advanced your condition is
• your overall health  

Unfortunately, many people are only diagnosed after the tumour has spread to other parts of the body.

However, it may still be possible to use surgery to remove the tumour. If surgery can't completely cure your condition, it may be used to help reduce and manage any symptoms.

Medication called somatostatin analogues, such as octreotide or lanreotide, may be recommended. They stop your body producing too many hormones, and can reduce the severity of your symptoms and slow the condition's progression. You'll have an injection, usually once every 28 days.

It may also be possible to shrink the tumour or stop it growing using treatments that block its blood supply (embolisation), or using chemotherapy, radiotherapy or radiofrequency ablation (where heat is used to destroy the cells).

There are also two treatments – everolimus and sunitinib – that can be used to treat some neuroendocrine tumours in adults if:

• they can't be fully removed using surgery
• they've spread
• the symptoms are getting worse

Everolimus is taken as a tablet, and sunitinib is taken as a capsule.

The National Institute for Health and Care Excellence (NICE) has more information about everolimus and sunitinib.

Cancer Research UK also has more information about neuroendocrine tumours.