A neuroendocrine tumour (NET) is a tumour that develops from cells of the neuroendocrine system. Cells that are similar to nerve cells make up the neuroendocrine system. They make chemical messengers called hormones. Hormones control how different organs in the body work.
Neuroendocrine cells are found throughout the body, in organs such as the stomach, bowel and lungs.
NETs can be non-cancerous (benign) or cancerous (malignant). This information is about malignant tumours. It is mainly about NETs affecting the digestive system.
Some NETs make extra hormones and cause symptoms. These are called functioning tumours. Tumours that do not make extra hormones are called non-functioning tumours.
NETs are grouped according to where the cancer started (the primary tumour). For example:
- small bowel NETs
- large bowel NETs
- appendix NETs
- pancreatic NETs
- stomach (gastric) NETs
- lung NETs.
Rarely, NETs occur in other areas, including the:
- bile ducts
You may hear some NETs referred to as carcinoid tumours. These are usually tumours of the digestive system or lungs.
NETs often grow slowly. They can be difficult to diagnose, as they may not cause symptoms for a long time. It may be several years before symptoms appear and the tumour is diagnosed. But some NETs grow faster and are more likely to spread to surrounding tissues and parts of the body.