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What are the symptoms?

Most NETs develop slowly over several years but they can also be aggressive and grow quickly, spreading to other parts of the body and causing problems.

In the early stages NETs may not cause symptoms. If you do have symptoms, it will depend on where in the body the tumour is and if the tumour cells are producing hormones. You may experience general symptoms such as fatigue and loss of appetite.


Symptoms may include:

  • abdominal (tummy) pain and bloating
  • changes in bowel or bladder habits, including diarrhoea
  • bowel obstruction or bleeding from the anus
  • facial flushing and asthma-like wheezing.


Functional NETs – produce extra amounts of hormones, and the first symptoms will often be related to this excess hormone production.

Symptoms may include:

  • low blood sugar levels (hypoglycaemia) causing shaking, sweating, confusion, dizziness and rapid heartbeat
  • high blood sugar levels (hyperglycaemia) which may cause increased urination, excessive thirst and blurred vision
  • indigestion (heartburn) and stomach ulcers
  • rash in the groin area
  • unexplained weight loss
  • nausea or vomiting
  • changes in bowel habits, including diarrhoea or pale, foul-smelling stools that are hard to flush away.

Non-functional NETs – do not produce extra hormones and rarely cause symptoms in the early stages. Symptoms often appear only once the cancer is large enough to affect nearby organs, or has spread (most commonly to the liver). As the tumour grows it may also cause pain in the upper abdomen, side or back.


Symptoms may include:

  • repeated pneumonia or chest infections
  • coughing up blood
  • shortness of breath; wheezing
  • chest pain.

Merkel cell carcinoma

This usually occurs as a painless hard nodule (tumour) in the skin that grows rapidly and is often red, purple or blue, or can be flesh-coloured. Some patients feel the nodule is under (rather than in) the skin. The most common location is skin that has been exposed heavily to the sun such as the face, head and neck.


Symptoms may include:

  • painless lump or swelling in the tummy, chest or neck
  • swollen legs, arms, upper chest, neck and face
  • loss of appetite or feeling full
  • weight loss
  • changes in bowel or bladder habits
  • difficulty breathing or swallowing
  • headaches or dizziness
  • drooping eyelid
  • trouble feeling or moving arms and legs.

Carcinoid syndrome

When NET tumours produce excess hormones (such as serotonin) it can cause a group of symptoms known as carcinoid syndrome. Some of these symptoms include facial flushing, diarrhoea, wheezing and carcinoid heart disease leading to shortness of breath.

It is most common in people with gastro-intestinal NETs, including duodenal and small bowel, and lung NETs that have spread (metastasised) in the body.  However, not all people with these NETs will develop the syndrome.

More information is available from NeuroEndocrine Cancer Australia.

Featured resources

Understanding Neuroendocrine Tumours

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Understanding Rare and Less Common Cancers

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This information is reviewed by

This information was last reviewed February 2021 by the following expert content reviewers: Dr David Chan, Medical Oncologist, Royal North Shore Hospital, NSW; Leslye Dunn, Consumer; Prof Gerald Fogarty, Radiation Oncologist, St Vincent’s Hospital, NSW; Katie Golden, Consumer; Dr Grace Kong, Nuclear Medicine Physician, Peter MacCallum Cancer Centre, VIC; Caitriona Nienaber, 13 11 20 Consultant, Cancer Council WA; Elizabeth Paton, Melanoma and Skin Cancer Trials Group, NSW.