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Everything you need to know about neuroendocrine tumors (NETs)

What Are NETs? What Causes NETs? Symptoms of NETs How Common Are NETs?

Types of NETs What May Happen Long Term? Your Care Team Questions to Ask Your Doctor

Diagnostic Tests Tumor Marker Tests

Imaging Methods Other Tests For NETs

Learn how to cope and live with neuroendocrine tumors (NETs)

Coping With Emotions Talking About NETs Gathering information about NETs Information For Caregivers

How are NETs treated? Liver-directed therapies Carcinoid syndrome treatments What to expect

Diet & Nutrition Keeping Track of Medical Care Traveling with NETs Working with NETs Managing Symptoms & Side Effects Hobbies & Interests Preparing for Imaging Scans Patient App

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Types of NETs

Neuroendocrine tumors (NETs) can be classified in several different ways:

The location in the body where NETs are found
The types of hormones they produce

Here you can read about the various types of NETs, which you may also hear referred to as carcinoid tumors, GI-NETs, GEP-NETs, pancreatic NETs, and lung NETs.

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
Gastrinomas	Gastrin	Zollinger-Ellison syndrome (ZES)	Diarrhea
Insulinomas	Insulin	Hypoglycemia syndrome	Confusion
			Forgetfulness
			Palpitations
			Hyperphagia
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.

Read about what may happen long term >