What are the types of neuroendocrine tumours?

There are a number of different types of NETs and ways of describing them. The type you have depends on the type of cell that the cancer started in. Most neuroendrocrine tumours are found in your digestive system. This includes your oesophagus, stomach, bowel, back passage (rectum) and appendix. NETs in other parts of your body are much rarer. These areas include your lungs, pancreas, kidneys, ovaries and testicles.

NETs can be grouped by where the tumour started in the body:

• Foregut: Lung, thymus, stomach, pancreas, first part of duodenum
• Midgut: Second part of duodenum, jejunum, ileum, right colon
• Hindgut: Transverse left, sigmoid colon, rectum

Functional and non-functional NETs

• Functional NETs: These produce extra hormones that cause symptoms
• Non-functional NETs: Do not cause hormone-related symptoms

Indolent and aggressive NETS

• Indolent: The tumour grows slowly.
• Aggressive: The tumour grows more quickly and is more likely to spread to other parts of the body.

Gastrointestinal (GI) NETs

GI NETs start in organs in the gastrointestinal (digestive) system tract. This includes the small bowel (small intestine), back passage (rectum), stomach, colon, oesophagus and appendix. GI NETs are a common type of NET. Most GI NETs grow slowly.

Types of GI NETs

• Functional GI NETs: Functional GI NETs are tumours that release excess hormones (particularly serotonin) and other chemicals into the blood. This can cause a group of symptoms known as carcinoid syndrome. Read more about GI NET symptoms and carcinoid syndrome.
• Well-differentiated GI NETs: The cells look much like normal cells. These tumours may be slow-growing (indolent) or faster-growing. Low-grade NETs are slower growing than high-grade NETs. Read more about grading NETs.
• Poorly differentiated GI NETs: The cells look very abnormal compared to normal cells. They tend to grow quickly and are more likely to spread.

Lung NETs

Lung NETs start in the lungs or the airways. For example, the bronchi that lead to the lungs from the windpipe. Lung NETs are a common type of neuroendocrine tumour.

Types of lung NETs

There are 4 types of lung NETs:

• Typical carcinoid tumours usually grow slowly (indolent) and don’t often spread to other parts of the body. The cells look and act much like normal cells.
• Atypical carcinoid tumours tend to grow slowly, but they may spread to other parts of the body. The cancer cells look and act much like normal cells (well differentiated).
• Large cell lung neuroendocrine carcinomas tend to grow quickly and are more likely to spread to other parts of the body. The cancer cells are very abnormal compared to normal cells (poorly differentiated).  
• Small cell lung neuroendocrine carcinomas, or small cell lung cancers, are also very abnormal compared to normal cells (poorly differentiated). They tend to grow quickly and often spread to other parts of the body.

Pancreatic neuroendocrine tumours (pNETs)

Pancreatic NETs can be functioning or non-functioning

• Functioning: The NET cells produce excess hormones, which can cause symptoms.
• Non-functioning: The NET cells don’t produce excess hormones.

Types of functioning pNETs

Functioning pNETs are often named after the hormone they produce. For example:

• Insulinoma
• Gastrinoma
• Somatostatinoma
• Glucagonoma
• VIPoma
• Pancreatic polypeptidoma

Well-differentiated / poorly differentiated pNETs

pNETs can also be grouped by how the cells look compared to normal cells and how fast the cells are growing:

• Well-differentiated pNETs: The cells are similar to normal cells. They tend to grow slowly.  
• Poorly differentiated pNETs: The cells are very abnormal compared to normal cells. They tend to grow quickly and have often spread to other parts of the body when they’re diagnosed.

Other neuroendocrine tumours

NETs can happen in other parts of the neuroendocrine system, but these NETs are very rare. For example:

• Adrenal glands (pheochromocytoma and paraganglioma)
• Thyroid gland (medullary carcinoma, parathyroid adenoma)
• Pituitary gland
• Thymus (thymic NET)
• Ovaries or testicles
• Skin (Merkel cell carcinoma)

If you need more information on any type of NETs, please call our Support Line on 1800 200 700. You can also look at our rare cancer page.