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.

Carcinoids – lung, thymic, gastric, duodenal, pancreatic, small intestine, appendiceal, colon, rectal, ovarian and carcinoid tumors of unknown origin (unknown primary).

Type of GEP-NET Hormone Secreted  Symptoms 
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” Serotonin Flushing, diarrhoea, cramps, wheezing, heart problems and skin changes

Pancreatic NET or pNET can be functioning (actively secreting hormones) or Non-functioning (no appreciable hormone production). These are futher 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.

Type of pNET Hormone Secreted  Symptoms 
Gastrinoma  Gastrin Oesophagitis, peptic ulcers, reflux, abdominal pain, vomiting
Zollinger–Ellison Syndrome
 Insulinoma Insulin Low blood sugar levels (hypolglycaemia) – sweating, headaches, dizziness, weakness, confusion, hunger, anxiety and shaking.
Somatostatinoma Somatostatin High blood sugar levels, low blood count (anaemia), diarrhoea, loss of weight
VIPoma  VIP (vasoactive intestinal polypeptide) Diarrhoea, weight loss, nausea, vomiting, fatigue, weakness.

Phaechromocytomas, these 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, closely related to phaeochromocytomas but 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.

Multiple endocrine Neoplasias (MEN)

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

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.

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.