What types of NETs are there?

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

  • Gastrointestinal NETs (GI-NETs)* are the most common type of NETs; these are found in the gastrointestinal (GI) tract (digestive system)
  • Pancreatic NETs (pNETs)* are formed in the islet cells of the pancreas, and include several uncommon types of NETs
  • Lung NETs account for about one quarter of NETs and are less common than other types

*NETs found in the gastrointestinal system or the pancreas are called gastroenteropancreatic NETs (GEP-NETs).

Areas in your body where NETs may appear

Diagram showing where neuroendocrine tumors (NETs, which you may also hear referred to as carcinoid tumors, GI-NETs, GEP-NETs, pancreatic NETs and lung NETs) may develop in the body.

Gastrointestinal NETs

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

NETs that occur in the GI tract or pancreas are sometimes grouped together and called gastroenteropancreatic neuroendocrine tumors, or GEP-NETs for short.

Pancreatic NETs

Pancreatic NETs (pNETs) may be classified as symptomatic or asymptomatic:

  • Symptomatic pancreatic tumors make extra amounts of hormones, such as gastrin, insulin, and glucagon, or other substances known as peptides, such as vasoactive intestinal polypeptide (VIP), that cause an associated syndrome or collection of identifiable symptoms in the body. Most symptomatic tumors are initially benign
  • Asymptomatic pancreatic tumors are mostly malignant at diagnosis. They may release certain hormones, but these do not cause an associated syndrome. Later on, these tumors may cause abdominal symptoms such as pain due to tumor 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 Hypoglycemia syndrome Confusion
VIPomas Vasoactive intestinal polypeptide (VIP) Verner-Morrison syndrome Watery diarrhea (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)
Diarrhea (bulky, greasy)
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 tumors)

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
  • Coughing up blood
  • Wheezing

Other types of NETs

Other rare NETs include those that start in the:

  • Thyroid gland – medullary thyroid tumors
  • Adrenal glands – known as paraganglioma-pheochromocytoma, a growth of tumors in structures (paraganglia) found near nerve cell bunches (ganglia)

Sometimes, it is impossible to determine where the NET has originally started; in this case it is called carcinoma of unknown primary origin.

Find out more about NETs

Diagnosis and Testing

Diagnosing NETs

Find out how NETs are diagnosed and the tools doctors may use to help.


Living with NETs

The emotional, physical, and social challenges of living with NETs.

Living with NETs

Advocacy & Support

Living with NETs is not something that you have to do alone. Find help and support.

Get support
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