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Neuroendocrine Tumours – benign vs malignant

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One of the most controversial aspects of Neuroendocrine Tumours (NETs) is the ‘benign vs malignant’ question.  It’s been widely debated and it frequently patrols the various patient forums and other social media platforms. It raises emotions and it triggers many responses ….. at least from those willing to engage in the conversation. At best, this issue can cause confusion, particularly to those who thought they had a handle on it. At worst, it might contradict what new patients have been told by their physicians (….or not been told). For some, it could cause some great concern and worry. In many ways, this topic is similar to the debate I raised in my blog ‘Incurable vs Terminal’.  You may benefit from reading this post before you move on.


To fully understand this issue, I’d like to cover some basic but widely accepted definitions of cancer.  I also need to bring the ‘C’ word into the equation (Carcinoid), because the history of these tumours is frequently where a lot of the confusion lies.  The use of the out of date term ‘Carcinoid’ confuses the issue given that it decodes to ‘carcinoma like’ which could infer not a proper cancer.  See more below.

Let’s look at these definitions provided by the National Cancer Institute.  I could have selected a number of organisations but in general, they all tend to agree with these definitions give or take a few words.  I supply these widely accepted definitions because there is an associated ‘tumour’ vs ‘cancer’ debate too.

Cancer – Cancer is the name given to a collection of related diseases. In all types of cancer, some of the body’s cells begin to divide without stopping and spread into surrounding tissues. There are more than 100 types of cancer which are usually named for the organs or tissues where the cancers form.  However, they also may be described by the type of cell that formed them.

Author’s note: The last sentence is important for Neuroendocrine Tumour awareness (i.e. Neuroendocrine Tumour of the Pancreas rather than Pancreatic Cancer).

Carcinoma – Carcinomas are the most common grouping of cancer types. They are formed by epithelial cells, which are the cells that cover the inside and outside surfaces of the body. There are many types of epithelial cells, which often have a column-like shape when viewed under a microscope.

Author’s note: By definition, Carcinomas are malignant, i.e. they are cancers. High Grade poorly differentiated “NETs” are deemed to be a ‘Carcinoma’ according to the most recent World Health Organisation (WHO) classification of Neuroendocrine Tumours (2017). You will have heard of some of the types of Carcinoma such as ‘Adenocarcinoma’ (incidentally, the term ‘Adeno’ simply means ‘gland’).

Malignant – Cancerous. Malignant cells can invade and destroy nearby tissue and spread to other parts of the body.

Benign – Not cancerous. Benign tumors may grow larger but do not spread to other parts of the body.

Author’s Note: This is a key definition because there are people out there who think that low grade NETs with metastasis is not cancer. 

Tumour (Tumor) – An abnormal mass of tissue that results when cells divide more than they should or do not die when they should. Tumors may be benign (not cancerous), or malignant (cancerous). Also called Neoplasm.

Author’s Note: Neoplasm is interesting as this is the term frequently used by ENETS and NANETS in their technical documentation, sometimes as a term to cover all Neuroendocrine grades of cancer (Tumor and Carcinoma). It follows that a malignant tumour is Cancer. The term “Malignant Neuroendocrine Tumour” is the same as saying “Neuroendocrine Cancer”

Neuroendocrine Tumours – Benign or Malignant?

Definitions out of the way, I have studied the ENETSUKINETS and NANETS guidance both of which are based on internationally recognised classification schemes (i.e. the World Health Organisation (WHO)).

In older versions of the WHO classification schemes (1980 and 2000), the words ‘benign’ and ‘uncertain behaviour’ were used for Grades 1 and 2. However, the 2010 edition, the classification is fundamentally different (as is the recent 2017 publication).  Firstly, it separated out grade and stage for the first time (stage would now be covered by internationally accepted staging systems such as TNM – Tumour, (Lymph) Nodes, Metastasis). Additionally, and this is key to the benign vs malignant discussion, the WHO 2010 classification is based on the concept that all NETs have malignant potential.  Here’s a quote from the UKINETS Guidelines in 2011 (Ramage, Caplin, Meyer, Grossman, et al). The guidance in 2017 WHO reinforces this statement.

Tumours should be classified according to the WHO 2010 classification (Bosman FT, Carneiro F, Hruban RH, et al. WHO Classification of Tumours of the Digestive System. Lyon: IARC, 2010). This classification is fundamentally different from the WHO 2000 classification scheme, as it no longer combines stage related information with the two-tiered system of well and poorly differentiated NETs. The WHO 2010 classification is based on the concept that all NETs have malignant potential, and has therefore abandoned the division into benign and malignant NETs and tumours of uncertain malignant potential.

The C Word (Carcinoid)

This is part of the problem!

History lesson – Carcinoid tumours were first identified as a specific, distinct type of growth in the mid-1800’s, and the name “karzinoide” was first applied in 1907 by German pathlogist Siegfried Oberndorfer in Europe in an attempt to designate these tumors as midway between carcinomas (cancers) and adenomas (benign tumors). The word ‘Carcinoid’ originates from the term ‘Carcinoma-like’.  ‘CARCIN’ is a truncation of Carcinoma (by definition cancerous or malignant tumour). ‘OID’ is a suffix used in medical parlance meaning ‘resembling’ or ‘like’.  This is why many people think that Carcinoid is not a proper cancer. We need to move away from the term ‘Carcinoid’ for this reason and as outlined in this post here.

Kunz His belief these tumors did not metastisize

How are NETs Classified?

If you read any NET support website it will normally begin by stating that Neuroendocrine Tumours constitute a heterogeneous group of tumours. This means they are a wide-ranging group of different types of tumours.  However, the latest WHO classification scheme uses the terms ‘Neuroendocrine Tumour’ for well differentiated Grade 1 (low-grade), Grade 2 (Intermediate Grade) and Grade 3a (High Grade); and ‘Neuroendocrine Carcinoma’ for Grade 3b or poorly differentiated tumours. They also use the term ‘Neoplasm’ to encompass all types of NET and NEC. So Grade 1 is a low-grade malignancy and so on (i.e any grade of NET is a malignant tumour).  You may benefit from reading my blog on Staging and Grading of NETs as this is also a poorly understood area.

But …….

By any accepted definition of cancer terms, a tumour can be non-cancerous (benign) or cancerous (malignant).  This is correct for any cancer type. For example, the word is used in the 2016 version of Inter Science Institute publication on Neuroendocrine Tumors, a document I frequently reference in my blog.  For example, I’ve seen statements such as “These tumors are most commonly benign (90%)” in relation to Insulinoma (a type of Pancreatic NET or pNET). Ditto for Pheochromocytoma (an adrenal gland NET).  Pituitary ‘adenomas’ are by definition benign (adenoma is the benign version of Adenocarcinoma).  And I note that there is a ‘benign’ code option for every single NET listed in the WHO International Classification of Diseases (ICD) system. Perhaps these organisations are just not up to date with the latest classification schemes for Neuroendocrine Disease?

The ‘BUT’ is this – all WHO classification systems are based on the concept that all NETs have malignant potential.

However …….

There’s a reason why the WHO declared in 2010 that all NETs have malignant potential (as amplified in WHO 2017). It may not happen or it may happen slowly over time but as Dr Richard Warner says, “they don’t all fulfill their malignant potential, but they all have that possible outcome”.  Thus why ongoing surveillance is important after any diagnosis of Neuroendocrine Tumour of any grade or at any stage.   Dr Lowell Anthony, a NET Specialist from the University of Kentucky explains this much better than I can – CLICK HERE to hear his two-minute video clip.


This was a difficult piece of research. However, based on the above, use of the word ‘benign’ is probably best used with great care given the 2010 and 2017 WHO classification of NETs.  Also I would certainly (at least) raise an eyebrow if someone said to anyone with any NET tumour, “you don’t need any treatment or surveillance for a NET”; or “it has been cured and no further treatment or surveillance is required”.  Particularly if they are not a NET specialist or a recognised NET Centre.

I do believe there are scenarios where NETs will be benign and probably never cause the person any real harm but SURVEILLANCE becomes really important due to the possibility that they all have malignant potential.  I also suspect this is the same for many cancers.

Remember, I’m not a medical professional, so if you are in any doubt as to the status of your NET, you should discuss this directly with your specialist.  A good place to start is evidence of your Grade, Differentiation, Primary Site Location and Stage.

You may benefit from reading these associated posts:

Benign vs Malignant

Carcinoid vs Neuroendocrine

10 Questions for your doctor

Thanks for listening


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Remember ….. in the war on Neuroendocrine Cancer, let’s not forget to win the battle for better quality of life!

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  1. Carol Bruce says:

    I have went misdiagnosed for 7 years effects my heart went to spine brain and because I caught dr’s lying through emails I’m not getting any treatment also in liver and pancreas went to go to gp asked to see oncologist she won’t refer me hospital won’t give me copy of disc. And she wants me to go and see people who misdiagnosed me in the first place. She said I could pay private and they would say anything so everyone is closing rankes. Flighting for my life and no one is listening.


  2. Hi Ronny

    To say I enjoy reading your blogs would be incorrect due to the nature of the beast, but I do find them easy to follow and understand. I have pancreatic primary leading to liver mestates which is still hanging around despite 2 resections. They dont scare me anymore after all, i am bigger than them and have a lot of people on my side. I dont think or ask how long have I got but more what shall i do today that is fun and makes me happy. Thank you so much for taking time out to help us understand better what is going on inside our bods. I am sure i speak for all your readers who really appreciate what you do. You should write a book! I would definately buy!!

    Liked by 1 person

  3. Gaynor Miles says:

    Thankyou again Ronny. Your writing is so much easier to understand

    Liked by 1 person

  4. cy says:

    Thanks. I have read a lot about NETS and this cleared up some confusion I had. There were things I did not know.

    Liked by 1 person

  5. edebock says:

    Thank you for doing the hard work and explaining things so clearly, Ronnie! This is the best explanation of the difference between benign and malignant that I have ever heard. As it pertains to NETS, this is information that definitely needs to be made better known. A couple of years ago, when I visited our local hospital emergency room for an issue completely unrelated to my NETS, the attending doctor, a locum, actually argued with me about whether or not I had cancer when I told him that I was a NETS patient!

    Liked by 1 person

  6. laurie says:

    Your words are always so well written and easy to understand. Thank you, again and again.

    Liked by 1 person

  7. jean borden says:

    Great explanation, Ronnie! Thanks, Jean Borden

    Liked by 1 person

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