What is
neuroendocrine cancer?
Understand what neuroendocrine cancer is, the different types and how they can affect the body
Overview
Neuroendocrine cancer is a less common type of cancer that can develop in different parts of the body. Because it is less common, many people have not heard of it before their diagnosis.
There are different types of neuroendocrine cancer, which can behave differently and may require different treatments. This page provides clear information to help you understand the basics of neuroendocrine cancer, some of the terms you may hear when talking to your healthcare team, and what they may mean for you.
You can take this information at your own pace; you do not need to read everything at once. Support is available when you need it.
What are neuroendocrine cells?
Neuroendocrine cancer starts in cells called neuroendocrine cells.
They are found throughout the body and help to regulate essential bodily functions such as breathing and digestion.
These cells receive signals from the nervous system, hence the ‘neuro’ part of the name.
After receiving a signal, they release hormones (biological messengers that travel throughout the body) instructing cells and organs what to do. The ‘endo’ part of the name refers to the ‘endocrine’ (or hormone) system.
If a neuroendocrine cell becomes cancerous, it can grow out of control and may produce too many hormones.
The endocrine and neuroendocrine system
Learn more about the endocrine and neuroendocrine system.
Types of neuroendocrine cancer
There are two main types of neuroendocrine cancer.
Neuroendocrine tumours (NETs)
These are called ‘well-differentiated’ cancers, meaning the cancer cells still look quite similar to normal neuroendocrine cells. They are usually (but not always) slow growing.
Up to half of NETs produce more hormones than normal neuroendocrine cells. These are what we call ‘functioning tumours’.
Neuroendocrine carcinomas (NECs)
These are called ‘poorly differentiated’ cancers, meaning they look very different from normal neuroendocrine cells, and are usually faster growing than NETs.
Almost all NECs are ‘non-functioning’. This means that they don’t produce more than normal levels of hormones.
The differences between NETs and NECs are important
They can influence:
- How these cancers grow
- The symptoms they may cause
- The treatments that may be offered
- How the condition may change over time
Understanding these differences – and accessing the right specialist care – can help ensure that you receive the most appropriate support for your individual situation.
Note: You may hear the term ‘carcinoid tumour’. This is an older term and refers to a well-differentiated NET (and, for now, is currently used when referring to lung or some less common NETs).
Where neuroendocrine cancers start
Neuroendocrine cancers can begin in many places around the body, but most often they start in the small intestine (bowel), the pancreas, and the lungs.
Where the cancer starts is called the primary site, and this helps doctors to understand how it behaves and how best to treat it.
How neuroendocrine cancer is diagnosed
Neuroendocrine cancer can be difficult to diagnose and is sometimes found during tests for other conditions. Diagnosis may involve a combination of blood or urine tests, scans, endoscopy and biopsy.
Understanding your diagnosis
Neuroendocrine cancers vary considerably from person to person. Your healthcare team may describe your cancer according to its type (NET or NEC), where it started (primary site), whether it produces excess hormones, its grade and its stage. Together, these characteristics help your team understand how your cancer may behave and how best to manage it.
Stage: How far the cancer has spread
The ‘stage’ describes whether cancer is localised to the primary cancer site or has spread to other places in the body.
Cancer is usually described as being at one of four stages, from stage I (one), where the tumour is small and contained at the primary site, to stage IV (four), where the cancer has spread to distant parts of the body (‘metastasised’).
The four stages of neuroendocrine cancers
Doctors also use the ‘TNM system’ to describe how far cancer has spread:
- T for ‘tumour’ describes the size of the main tumour and how far it has grown.
- N for ‘node’ describes whether the cancer has spread to nearby lymph nodes.
- M for ‘Metastasis’ describes whether the cancer has spread to distant parts of the body.
‘Metastatic’ cancer means that the cancer has spread from its primary site to another part of the body. Even if it spreads, it is still the same type of cancer. For example, if a neuroendocrine cancer starts in the pancreas and spreads to the liver, it is still called pancreatic neuroendocrine cancer, not liver cancer.
Grade: How fast the cancer is growing
Doctors look at how quickly cancer cells are growing and dividing in order to ‘grade’ the tumour.
Grade 1 cancers are the slowest growing and grade 3 cancers are the fastest growing.
Neuroendocrine tumours (NETs) are graded 1 to 3, while neuroendocrine carcinomas (NECs) are all graded 3.
Measuring how fast a cancer is growing
The ‘proliferation rate’ helps doctors to determine the grade of the tumour – how slow or quickly it is growing.
To measure the proliferation rate, a small sample of the tumour is checked in a laboratory for two key features:
- Mitotic rate: This counts how many cells are dividing in a set area under the microscope.
- Ki-67: This is a protein found in growing cells. The higher the Ki-67 percentage, the more rapidly the cells are dividing and growing.
You may see these results in your pathology report as:
- Mitoses per 10 HPF (high-power fields under the microscope)
- Ki-67 percentage (%)
NETs are well differentiated and can be graded 1–3
- Grade 1 (slow): Ki-67 is less than 3% (less than 2 mitoses per 10 HPF)
- Grade 2 (medium): Ki-67 is 3–20% (2–20 mitosis per 10 HPF)
- Grade 3 (fast): Ki-67 is above 20% (above 20 mitoses per 10 HPF)
NECs are poorly differentiated and are all grade 3: the KI-67 is always above 20%, and is often above 50% (above 20 mitoses per 10 HPF).
This is important because the differences between NET and NEC can influence how these cancers grow, what symptoms they cause, and how they may be treated.
Is neuroendocrine cancer inherited
Most neuroendocrine cancers are not inherited, but a small number are linked to rare genetic conditions. Genetic testing can be used to determine if you have an inherited condition. This can sometimes be relevant to your care and may also have implications for family members.
Conditions associated with neuroendocrine cancer
- Multiple endocrine neoplasia (MEN types 1–5)
- Familial medullary thyroid cancer (FMTC)
- Familial phaeochromocytoma (or paraganglioma)
- Parathyroid hyperplasia
- Familial isolated pituitary adenoma (FIPA)
- Succinate dehydrogenase (SDH)–related conditions
- Von Hippel–Lindau (VHL) syndrome
- Neurofibromatosis type 1 (NF1)
You can find out more about genetic conditions linked to neuroendocrine cancer at the Association for Multiple Endocrine Neoplasia Disorders (AMEND).
Treatment for neuroendocrine cancer
Treatment for neuroendocrine cancer depends on your individual diagnosis and circumstances.
Options may include:
- Surgery: to remove all or part of the tumour
- Medicines: including hormone therapy or chemotherapy
- Endoscopic therapy
- Radiotherapy
- Targeted or specialised treatments
- Supportive care to manage symptoms
You may have one or a combination of treatments.
Support and next steps
Living with neuroendocrine cancer can bring practical and emotional challenges, and support is available.
You do not have to face this alone. Support is here when you are ready.
This information is designed to help you understand neuroendocrine cancer. It does not replace advice from your specialist healthcare team, who know your individual situation best.
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