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Types of Neuroendocrine Tumours

Neuroendocrine Tumours (NETs) is an umbrella name for a number of different types of tumours, which can arise in different areas of the body. It can be overwhelming to understand this complicated disease but we will try to help break in down.

There are a number of different types of NETs and they all have a slightly different way of presenting themselves, both in terms of symptoms and how they look under a microscope (histology).


The naming of NET tumours is derived from the anatomical area from which they are found in the body and some are named based on the predominant hormone that they secrete.

Gastrointestinal NETs

Gastrointestinal neuroendocrine tumours (GI NET) are a rare type of cancer that can start in different parts of your digestive system, called the GI system. The GI system includes the stomach, small intestine, colon, and rectum.

​Types of Gastrointestinal NETs (GI NETs)

  • Non functioning (non hormone secreting)

    • Symptoms of these non functioning NETs relate to their size and resultant localised pressure effects on other organs.

  • Functioning (hormone secreting) “carcinoid syndrome"

    • Hormone released: serotonin

    • Symptoms: Flushing, diarrhoea, cramps, wheezing, heart problems and skin change

Pancreatic NETs

PNETs are types of tumours that can be functioning (actively secreting hormones) or Non-functioning (no appreciable hormone production). These are further subdivided into types that indicate the hormones they produce. Unfortunately the non functioning pancreatic NETs secrete certain hormones and peptides like other NETs but the release of these chemicals does not cause an identifiable syndrome or collection of symptoms. This can make diagnosis difficult and explains why so many cases are picked up incidentally.

Types of PNETs:

  • Gastrinoma

    • Hormone secreted: Gastrin

    • Symptoms: Oesophagitis, peptic ulcers, reflux, abdominal pain, vomiting

  • Insulinoma

    • Hormone secreted: Insulin

    • Symptoms: Low blood sugar levels (hypolglycaemia) – sweating, headaches, dizziness, weakness, confusion, hunger, anxiety and shaking.


  • Somatostatinoma

    • Hormone secreted: Somatostatin

    • Symptoms: High blood sugar levels, low blood count (anaemia), diarrhoea, loss of weight


  • VIPoma

    • Hormone secreted: VIP (vasoactive intestinal polypeptide)

    • Symptoms: Diarrhoea, weight loss, nausea, vomiting, fatigue, weakness.

Lung NETs

Neuroendocrine cells are present throughout the lungs or respiratory tract. Lung Neuroendocine cancers account for up to 20% of all lung cancers.  They are often called Carcinoid tumours of the lung. 

There are 5 types of Lung neuroendocrine tumours 

  • Typical Carcinoid (TC) low grade neuroendocrine tumour (NET) 

  • Atypical Carcinoid (AC) mid-grade neuroendocrine tumour (NET) 

  • Small cell neuroendocrine carcinoma (NEC) 

  • Large cell neuroendocrine carcinoma (NEC) 

  • MiNEN or mixed cell carcinoma (MiNEN) – where Neuroendocrine cells occur within the same tumour as another form of cancer. 

Adrenal NETs

The adrenal glands are hormone producing organs that sit on top of the kidneys. The outer part is called the cortex, responsible for producing glucocorticoids and mineralocorticoids – (cortisol and aldosterone) as well as small amounts of male and female sex hormones. 

Adrenocorticol Carcinoma (ACC)

Adrenocorticol Carcinoma (ACC) is a cancer that starts in the cortex – the outer layer of the adrenal gland and affect cortisone and aldosterone production.  

The inner part of the adrenal gland is called the medulla – responsible for producing adrenaline and noradrenaline. These are the fight or flight hormones, which are released when the sympathetic nervous system recognises physical or emotional stress. 


Phaeochromocytomas are tumours of the adrenal glands (located on top of the kidneys) and can actively secrete noradrenaline and adrenaline causing symptoms such as high blood pressure, palpitations, sweating, nervousness, headaches, loss of weight.


Paragangliomas arise along the sympathetic chain. Present as painless masses but some secrete adrenaline and noradrenaline. 1-3% can metastasise. Up to 30% of paragangliomas are inherited.

Why do NET cancers behave differently in different people?

Different NETs affect people in different ways in terms of how the tumour grows, the symptoms produced, whether or not they spread and how they spread. However, all NETs share some similar characteristics.

The histology (what the tumours look like under a microscope) is very important in order to classify the cancer into a type, and therefore allow the medical team to be able to plan appropriate treatment. Although NETs share similar characteristics, the diagnosis and the way the cancer may behave could be different.

Merkel cell carcinoma

Merkel cell carcinoma, or primary neuroendocrine carcinoma of skin occur are tumours that appear as firm, painless reddish coloured nodules particularly on sun exposed areas of skin. They can grow rapidly and can metastasise to other organs.

Multiple endocrine Neoplasia Type 1 (MEN1)

Multiple endocrine Neoplasia Type 1 (MEN1) is a genetic condition which most often affects, (but not limited to) the parathyroids, pituitary, pancreas and thymus glands. Often tumours can also arise in the gastrointestinal tract. If you have had a family member who has a NET or passed away from an 'uncommon cancer' then it is worth talking to your health care provider about your family history. This can be diagnosed simply by having a genetic blood test. It is important to be diagnosed early to ensure tumours are picked up as soon as they arise. International guidelines suggest testing children of an affected parent from 5 years of age.

Appendiceal NETs

The appendix is a small tube found near the junction where the large and small bowel meet in the lower right abdomen. It has no clearly identified function in humans. 

Appendiceal Neuroendocrine Cancers, less than 1cm, completely removed by surgery, often do not need any further treatment or follow up – they are essentially cured. However, if the cancer is larger, shows evidence of spread, is found at the base of the appendix or the appendix has ‘burst’, you may need further follow up and/or treatment. 

For Appendiceal NETs with lower grade histology this may require further surgery, whereas for Appendiceal NECs with higher grading this may involve surgery with or without chemotherapy. 


The most important aspect of NET patient care is that it is tailored to suit the individual, and that this care is provided by a specialist in the field of NETs. Quality of life is paramount for the patient, and so teamwork is essential to provide a solid plan of treatment and follow-up.


There has been much research work done by specialist healthcare professionals and progress has been made in terms of understanding these tumours. It is important to ensure that people with NETs are seen by specialists in order to access all the knowledge available.

A NET cancer patient should ideally be referred to a centre where there is a multidisciplinary team that works together to ensure the best outcomes for each patient. This team would normally include gastroenterologists, surgeons, oncologists, endocrinologists, radiologists, nuclear medicine specialists, histopathologists and clinical nurse specialists.

If you have any questions, please email our Information and Support Manager, Avril Hull:

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