They can also affect the lung, pancreas, kidney, ovaries or testicles and may spread to the liver.
These cancers arise from the neuroendocrine system, which is made up of nerve and gland cells that make hormones and release them in to the bloodstream. Most of these tumours occur by chance, but some can be inherited as part of a syndrome (Multiple Endocrine Neoplasia - MEN type 1).
Neuro-endocrine tumours of the bowel may have no symptoms, but can cause abdominal pain and blockages of the bowel or watery diarrhoea. Some of these tumours produce large amounts of hormones that can cause flushing of the skin, abdominal pain, diarrhoea, loss of appetite, fast heart rate, wheezing or dizziness due to blood pressure. This is also known as the 'carcinoid syndrome'.
Treatment of these tumours often depends on how early they are detected. Surgery to remove the tumour is often the most effective treatment but is not always possible. Other treatments include chemotherapy, radiotherapy, somatostatin analogues, reducing the tumour's blood supply by embolization, and reducing its size by radiofrequency ablation. Decisions on treatments and surveillance of these tumours should be undertaken at a specialist neuroendocrine centre of excellence such as The Christie.