What are neuroendocrine cancers?

Neuroendocrine tumours (NETs) and neuroendocrine carcinomas (NETs)

Your healthcare team might call your cancer a neuroendocrine neoplasm (NEN). The term NEN means the same thing as neuroendocrine cancer. There are 2 key groups of NENs: 

• Neuroendocrine tumours (NETs) can be slow, moderate or fast growing cancers. Their cells are abnormal but they look quite similar to normal neuroendocrine cells. 

• Neuroendocrine carcinomas (NECs) are all fast growing cancers. Their cells look very different to normal neuroendocrine cells. 

You might hear some doctors or nurses use the term Carcinoid, instead of NET. This is an old term which doctors don't use very often anymore.

The wording we use to describe these cancers has changed over time. This is because of improvements in our understanding about these cancers. 

The neuroendocrine system

The neuroendocrine system is made up of nerve pathways and neuroendocrine cells.

You have neuroendocrine cells throughout your body. Your brain sends these nerve signals. In response they make and release hormones and similar substances. These keep our bodies working properly.

• The term neuro refers to nerve signalling and response.

• The term endocrine refers to making and releasing ​hormones.​  

Hormones (and similar substances) are essential for normal human development and growth. They also help with different body functions. For example they help with breathing, digesting and sleeping. And they help with our body's response to stressful situations.

There are neuroendocrine cells throughout the body. They are in almost all organs and ​endocrine glands​ including your:

• food pipe (oesophagus)

• stomach

• lungs

• small and large bowel

• pancreas

• appendix

Find out more about the endocrine system

What do neuroendocrine cells do?

Neuroendocrine cells have different effects on the body. These depend on:

• where they are in the body

• what hormones they produce

• how much hormone they release

For example, neuroendocrine cells in the small bowel make a hormone called ​serotonin​. Serotonin helps to control the muscles that move food through the bowel. 

When cancer starts within neuroendocrine cells, it changes how the cells grow. And it can change how they work. They can grow out of control and might produce higher than normal levels of hormone.

What are the differences between NETs and NECs?

A specialist doctor (​pathologist​) looks at the cancer cells under a microscope. They report how:

• abnormal the cells look – doctors call this differentiation

• quickly or slowly the cancer cells are dividing and growing – doctors call this grading

Neuroendocrine Tumours (NETs)

• NETs are well differentiated cancers. This means they look abnormal. But they still have some similarities to normal neuroendocrine cells.

• NETs may be grade 1, 2 or 3. This means they can be slow, medium or fast growing.

Neuroendocrine Carcinomas (NECs)

• NECs are poorly differentiated cancers. This means they look very abnormal. They are not like normal neuroendocrine cells at all.

• NECs may be small cell or large cell in appearance.

• Doctors don't usually give NECs a grade. This is because they all grow quickly. 

Read about neuroendocrine carcinoma (NEC)

How doctors group neuroendocrine cancers

Doctors put your neuroendocrine cancers into one of the 2 key groups: a neuroendocrine tumour (NET) or a neuroendocrine carcinoma (NEC).

They also group your neuroendocrine cancer depending on:

• where it develops – this is called the primary site

• how far it has spread – this is called the stage

• whether it makes and releases abnormal levels of hormones - this is called functioning or non functioning

The primary site

Neuroendocrine cancers can develop in different parts of the body. Doctors group them, depending on the place they start growing. For example, a lung neuroendocrine cancer starts in the lung.

The place where the cancer starts is the primary cancer. If the cancer spreads to another part of the body, it’s called a secondary cancer. 

Around 40 out of every 100 neuroendocrine cancers (around 40%) start in the ​digestive system​. This is also called the gastrointestinal (GI) system. It includes the:

• stomach

• small bowel (duodenum, jejunum, and ileum)

• large bowel (colon)

• pancreas

• back passage (rectum)

Around 20 out of every 100 neuroendocrine cancers (around 20%) start in the lung.

Neuroendocrine cancers can also start in other places such as the:

• food pipe (oesophagus)

• appendix

• skin

• prostate

• womb

• adrenal, parathyroid and pituitary glands

In some cases, doctors do not know where the original neuroendocrine cancer started. This is called cancer of unknown primary (CUP).

ChooseRead about your type of neuroendocrine cancer

The stage

The stage refers to how big your neuroendocrine cancer is, and how far it has spread. There are different ways of describing your stage. This depends on where the neuroendocrine cancer started to grow (the primary site).

Your doctor might refer to your neuroendocrine cancer as:

• early stage – it has stayed in the area where it started

• advanced stage – it has spread to other parts of your body

Or they might give it a number stage between stage 1 and stage 4.

Read more about staging neuroendocrine cancer

Functioning and non functioning neuroendocrine tumours (NETs)

Cancer can disrupt how much hormone the neuroendocrine cells make. It is much more common for NETs to produce abnormal levels of hormones than NECs.

Doctors sometimes group NETs depending on whether they make abnormal levels of hormones:

How common are neuroendocrine cancers?

Neuroendocrine cancers are rare. Around 4,100 people are diagnosed with a neuroendocrine cancer each year in the England. They are getting more common across the world. This might be because there are better tests to diagnose them. 

Find out about tests for neuroendocrine cancers