This website is intended for an international audience, excluding the UK, United States, Canada and France
This website is intended for an international audience, excluding the UK, United States, Canada and France

The three main areas where NETs originate from in the body are the gastrointestinal tract (digestive system), the pancreas and the lungs.

  • Gastrointestinal NETs (GI-NETs)
    GI-NETs are the most common type of NETs and can be found anywhere in the gastrointestinal (GI) tract (digestive system). This includes in the small intestine, stomach, large intestine, rectum, duodenum and appendix.
  • Pancreatic NETs (pNETs)
    Pancreatic NETs are formed from the islet cells of the pancreas and include several uncommon types of NETs.
  • Gastroenteropancreatic NETs (GEP-NETs)
    When NETs are found in both the digestive system and the pancreas these are referred to as GEP-NETs.
  • Lung NETs
    Lung NETs account for about one quarter of NETs.
  • Other sites
    Other uncommon sites of NETs include the female reproductive system, other endocrine glands, and the ear, nose and throat.

Areas in your body where NETs may appear

Diagram showing where neuroendocrine tumours (NETs) may develop in the body.

Gastrointestinal NETs

Gastrointestinal NETs (GI-NETs) are the most common type of NETs (previously called carcinoid tumours). They are found in the gastrointestinal (GI) tract, including tumours that develop in the small intestine, the appendix, the stomach, the oesophagus, the colon and the rectum.

NETs that occur in the GI tract or pancreas are sometimes grouped together and called gastroenteropancreatic neuroendocrine tumours or GEP NETs for short. The combined number of GEP-NETs cases is now ranked as the second most prevalent gastrointestinal cancer, after colon cancer.

Pancreatic NETs

Pancreatic NETs (pNETs) may be classified as functioning tumours or non-functioning tumours:

Functioning pancreatic NETs make extra amounts of hormones, such as gastrin, insulin and glucagon, or other substances known as peptides, such as vasoactive intestinal peptide (VIP), that cause an associated syndrome – or collection of identifiable symptoms in the body.

Non-functioning pancreatic NETs account for the majority of pancreatic NETs. Most non-functioning pancreatic tumours are malignant at diagnosis. They may release certain hormones but these do not cause an associated syndrome. Later on, these tumours may cause abdominal symptoms such as pain due to tumour growth.

There are several subtypes of pancreatic NETs. Each is named according to the type of hormone or substance they produce, as shown in the table below.

Pancreatic NET types Main hormone or substance involved Associated syndrome Major symptoms
Gastrinomas Gastrin Zollinger-Ellison syndrome (ZES) Ulcers
Insulinomas Insulin Hypoglycaemia syndrome Very low blood sugar
Weight gain
Insulin resistance
VIPomas Vasoactive intestinal peptide (VIP) Verner-Morrison syndrome Watery diarrhoea (pancreatic cholera), which can cause potassium deficiency in the blood or reduced acid secretion in the stomach
Glucagonomas Glucagon n/a Rash
Glucose intolerance (diabetes)
Weight loss
Somatostatinoma Somatostatin n/a High blood sugar (glucose)
Diarrhoea (bulky, greasy)
Reduced acid secretion in the stomach
Weight loss


Lung NETs

Lung NETs account for around one quarter of all NETs. Within this group there are two major types:

  • Typical carcinoids
  • Atypical carcinoids – these are faster progressing tumours

The most frequent symptoms of lung NETs are very common in other conditions, which can make lung NETs very difficult to diagnose.

These symptoms include:

  • Coughing
  • Chest pain
  • Shortness of breath
  • Coughing up blood
  • Fever
  • Wheezing

Other types of NETs

Other rare NETs include those that start in the:

  • Thyroid gland – medullary thyroid tumours
  • Skin – Merkel cell cancer
  • Adrenal glands – (e.g. pheochromocytoma)
  • Thymus
  • Other organs like breast, prostate and kidney

In about 10% of cases it is impossible to determine where the NET has originally started; in this case it is called cancer of unknown primary origin.


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This website is intended for an international audience, excluding the UK, United States, Canada and France. This website has been developed by Ipsen in collaboration with those living with NETs and the healthcare professionals who care for them. Ipsen would like to thank everyone for their valuable insights and stories. All names used on this website are not necessarily real names. Visit for more information about us. Website design and development by Kanga Health Ltd. ALL-ALL-002300/November 2020