Signs and symptoms

Symptoms will depend on where in the body the neuroendocrine tumour (NET) is.

Symptoms of a NET in the digestive system may include:

  • pain or discomfort in the tummy area (abdomen) that comes and goes
  • feeling sick (nausea) or being sick (vomiting)
  • diarrhoea
  • heartburn and indigestion.

A NET in the lung may cause:

  • chest infections
  • shortness of breath
  • a cough
  • coughing up blood.

Loss of appetite and weight loss may also be symptoms of a neuroendocrine tumour.

NETs sometimes make too much of certain hormones. When the hormones are released into the blood stream, they cause symptoms. These NETs are called functioning tumours.The type of hormone they make depends on which gland the tumour is affecting.

Some hormone producing NETS may cause a collection of symptoms that include diarrhoea and flushing.  This is called carcinoid syndrome. This is more likely to happen with digestive system NETS.  

Some other rare hormone producing NETS include: 

  • insulinomas
  • gastrinomas
  • glucagonomas
  • VIPomas
  • somatostatinomas.


Insulinomas are tumours that can develop in any part of the pancreas. The pancreas makes insulin, which controls the level of sugar in the blood. If you have an insulinoma, the tumour makes an unusually high level of insulin. This causes low blood sugar levels (hypoglycaemia).

A low blood sugar level may cause symptoms such as:

  • headaches and dizziness
  • confusion and anxiety
  • trembling and palpitations
  • eyesight changes
  • feeling hungry or weak
  • fits (seizures).

A low blood sugar level is most likely to occur:

  • first thing in the morning
  • when exercising
  • after missing a meal.

Often eating or having a sugary drink will raise the blood sugar level again.


Gastrinomas are tumours that usually start in the pancreas or the upper part of the small bowel (duodenum). They sometimes make too much gastrin. Gastrin is a hormone that controls the amount of gastric acid that the stomach makes.

Too much gastrin causes the stomach to make more gastric acid. High levels of gastric acid can lead to sores (ulcers) in the stomach, the gullet (oesophagus) and the small bowel. There may be several ulcers. Often, these do not respond well to the usual medicines. This is often called Zollinger-Ellison syndrome.

Common symptoms of a gastrinoma include:

  • feeling bloated or pain in the tummy area (abdomen)
  • diarrhoea
  • heartburn
  • weight loss
  • bleeding into the stomach
  • feeling sick (nausea) or being sick (vomiting).


These tumours are usually in the pancreas. They usually make too much glucagon, a hormone that helps control blood-sugar levels.

Common symptoms of a glucagonoma include:

  • anaemia (a low level of red blood cells)
  • weight loss
  • high blood-sugar (hyperglycaemia)
  • a skin rash
  • diarrhoea
  • blood clots.


These tumours are usually in the pancreas. They may make too much of a substance called vasoactive intestinal peptide (VIP).

Common symptoms of a VIPoma include:

  • watery diarrhoea
  • low levels of potassium because of the diarrhoea
  • feeling weak and tired
  • feeling sick (nausea) and being sick (vomiting).


Somatostatinomas are rare tumours. They are usually in the pancreas or parts of the small bowel (the duodenum or jejunum). They make extra somatostatin. This is a hormone that stops the pancreas producing other hormones. Somatostatin also affects how the digestive system works.

Common symptoms of a somatostatinoma include:

  • pain in the tummy area (abdomen)
  • weight loss
  • pale, greasy and offensive-smelling poo (steatorrhoea)
  • diarrhoea
  • high blood-sugar (diabetes)
  • yellowing of the skin and whites of the eyes (jaundice).

NETs that do not cause symptoms

Some tumours do not overproduce hormones and may not cause symptoms. These are known as non-functioning NETs. They may show up during operations or tests that you are having for other reasons.

About our information

  • Reviewers

    This information has been written, revised and edited by Macmillan Cancer Support’s Cancer Information Development team. It has been reviewed by expert medical and health professionals and people living with cancer. It has been approved by Chief Medical Editor, Professor Tim Iveson, Consultant Medical Oncologist.

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