What are the types of neuroendocrine tumours?

There are a number of different types of NETs and ways of describing them.

Functioning or non-functioning 

• Functioning NETs: These produce extra hormones that cause symptoms.
• Non-functioning NETs: Do not cause hormone-related symptoms.

Indolent or aggressive 

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

Where did the NET develop?

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

• Functioning GI NETs
  Functioning 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 NET symptoms and carcinoid syndrome.
• Well-differentiated GI NETs
  The cells look 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.

Your medical team may use different terms to describe lung NETs. For example, bronchial NET, pulmonary NET. Ask them if you have questions about your diagnosis. 

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.

Functioning lung NETs

Functioning lung NETs cause symptoms related to hormones. For example, carcinoid syndrome and Cushing syndrome. Cushing syndrome is caused by too much of the hormone cortisol. It is rare and causes symptoms such as weight gain and a round, red face. 

Your medical team will give you information about symptoms if you have a functioning lung NET. You can also read more about NET symptoms 

Pancreatic neuroendocrine tumours (pNETs)

Functioning or non-functioning pNETs

• 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, an insulinoma produces the hormone insulin, a gastrinoma produces the hormone gastrin. 

The symptoms from functioning pNETs mainly depend on the type of hormone released. 

Your medical team will give you information about symptoms if you have a functioning lpNET. You can also read more about NET symptoms 

Well-differentiated or 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)

Ask your treating team how these NETs might affect you. 

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.