Learn how neuroendocrine tumours (NETs) develop and the importance of diagnosis and treatment in managing this rare condition.
Learn more about:
- What are neuroendocrine tumours (NETs)?
- The different types of NETs
- How common are NETs?
- What causes NETs?
What are NETs?
The neuroendocrine system is made up of many glands and nerve cells all over the body that produce hormones and then release them into the bloodstream. These hormones help control how the body works, for example, in digesting food.
NETs, also called neuroendocrine neoplasms (NENs), are a rare group of tumours that develop from neuroendocrine cells that become abnormal and keep growing. All NETs are considered cancer (malignant), but some grow slowly (low grade) while some grow quickly (high grade). The high grade tumours are also known as neuroendocrine carcinomas (NECs).
Malignant tumours can spread through the bloodstream or lymph vessels and form another tumour at other parts of the body. This new tumour is known as secondary cancer or metastasis.
The different types of NETs
NETs are grouped according to where in the body the cancer started. Some NETs make extra hormones, which can cause certain symptoms. These are referred to as functional tumours.
NETs that do not produce extra hormones are known as non-functional tumours.
Gastro-intestinal
These NETs start in the gastrointestinal (GI) tract, which is part of the digestive system. They include:
- gastric NETs, in the stomach
- duodenal NETs
- small bowel NETs, including the jejunum and ileum
- large bowel NETs, in the colon
- appendiceal NETs
- rectal NETs, near the anus.
Pancreatic
The pancreas is a long, flat gland that lies between your stomach and spine. It makes digestive juices and hormones.
Pancreatic NETs start in the neuroendocrine cells of the pancreas and make up about 5% of cancers in the pancreas. Most (about 90%) of pancreatic NETs do not produce extra hormones and are called non-functioning.
Functional pancreatic NETs are rare and most are named after the hormone they overproduce:
- insulinomas produce too much insulin
- glucagonomas produce too much glucagon
- gastrinomas produce too much gastrin
- somatostatinomas produce too much somatostatin
- VIPomas produce too much of a substance called vasoactive intestinal peptide.
Lung
Lung NETs make up about 14% of lung cancers.1 The 4 subtypes of lung NETs are:
- typical carcinoids
- atypical carcinoids
- large cell neuroendocrine carcinomas
- small cell lung neuroendocrine cancer.
Other types of NETs
Merkel cell carcinoma is a fast-growing cancer in cells in the top layer of the skin. For a directory of specialists in Merkel cell carcinoma care and treatment, visit the Australian Merkel Cell Carcinoma Interest Group.
Neuroblastoma, a tumour in the adrenal glands above the kidneys, is more commonly diagnosed in children. For more information, contact Neuroblastoma Australia.
For more information on other types of NETs, including thymic, testicular, prostate, ovarian and endometrial, multiple endocrine neoplasia (MEN), pheochromocytoma, paraganglioma and medullary thyroid carcinoma, visit NeuroEndocrine Cancer Australia.
Where are NETs mainly found?
This diagram shows the places where NETs are typically found.
How common are NETs?
NETs are not common but the number of people being diagnosed is slowly increasing. There is an almost equal risk for males and females.
Around 5700 Australians are diagnosed with a specific NET each year, with most new cases being diagnosed in people aged 40 years or over.
What causes NETs?
The causes of most NETs are not known. However, some factors increase the risk of developing certain types of NETs. Having these risk factors does not mean you will develop a NET, but if you are concerned, talk to your doctor.
Genetic conditions and NETs
People with some rare, inherited diseases have a higher risk of NETs.
These conditions include:
- multiple endocrine neoplasia (MEN 1, MEN 2)
- Von Hippel- Lindau (VHL) syndrome
- tuberous sclerosis complex (TSC)
- neurofibromatosis (NF).
Other risk factors
Some NETs are more likely in certain people, such as those who have:
- conditions that affect stomach acid, such as pernicious anaemia, peptic ulcers and chronic atrophic gastritis
- inflammatory bowel disease
- diabetes – which may increase the risk of pancreatic NETs
- exposure to cancer-causing substances
- certain gene mutations, such as succinate dehydrogenase subunit genes (SDHx), which can increase the risk of tumours, paragangliomas and phaeos in the kidneys and GI tract.
Specific NETs can occur in certain age groups, such as appendiceal NETs in younger people, neuroblastoma in children under 5, or Merkel cell carcinoma in older men.
For an overview of what to expect at every stage of your cancer care, visit Neuroendocrine tumours: Your guide to best cancer care. This is a short guide to what is recommended, from diagnosis to treatment and beyond.
→ READ MORE: What are NETs symptoms?
Prof Michael Michael, Gastrointestinal and Neuroendocrine Medical Oncologist and Co-Chair Neuroendocrine Unit, Peter MacCallum Cancer Centre, VIC; Tracey Bilson, Consumer; Meredith Cummins and Kahlia Wolsley, NeuroEndocrine Cancer Australia; Dr Ganessan Kichenadasse, Medical Oncologist and Pharmacologist, Flinders Medical Centre, SA; Dr Nat Lenzo, Nuclear Medicine Physician, ICON, WA; A/Prof David Pattison, Co-Director, Department of Nuclear Medicine & PET Services, Royal Brisbane & Women’s Hospital, QLD; Prof Jas Samra, Head of Upper GI Surgery, RNSH and Clinical Prof of Surgery, University of Sydney, NSW; Jillian van Zijl, 131120 Consultant, Cancer Council WA; A/Prof David Wyld, Director, Medical Oncology, Royal Brisbane & Women’s Hospital, QLD.
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