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, at worst, it might contradict what new patients have been told by their physicians (….or not been told). I don’t believe it’s an exact science and can be challenging for a NET specialist let alone a doctor who is not familiar with the disease.
NANETS Guidance talks about the ‘…heterogeneous clinical presentations and varying degrees of aggressiveness‘ and ‘…there are many aspects to the treatment of neuroendocrine tumours that remain unclear and controversial‘. I’m sure the ‘benign vs malignant’ issue plays a part in these statements.
In another example, ENETS Guidance discusses (e.g.) Small Intestine Tumours (Si-NETs) stating that they ‘derive from serotonin-producing enterochromaffin cells. The biology of these tumors is different from other NENs of the digestive tract, characterized by a low proliferation rate [the vast majority are grade 1 (G1) and G2], they are often indolent’. However, they then go on to say that ‘Si-NETs are often discovered at an advanced disease stage – regional disease (36%) and distant metastasis (48%) are present‘. It follows that the term ‘indolent‘ does not mean they are not dangerous and can be ignored and written off as ‘benign’. This presents a huge challenge to physicians when deciding whether to cut or not to cut.
To fully understand this issue, I studied some basic (but very 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 The use of the out of date term ‘Carcinoid’ exacerbates the issue given that it decodes to ‘carcinoma like‘ which infers it is not a proper cancer. See more below.
Let’s look at these definitions provided by the National Cancer Institute. Please note 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. These definitions help with understanding as there can be 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 (Grade 3) poorly differentiated “NETs” are deemed to be a ‘Carcinoma’ according to the most recent World Health Organisation (WHO) classification of Neuroendocrine Tumours (2017) and ENETS 2016 Guidance. You will have heard of some of the types of Carcinoma such as ‘Adenocarcinoma’ (incidentally, the term ‘Adeno’ simply means ‘gland’). It follows that Grade 3 Neuroendocrine Carcinomas are beyond the scope of this discussion.
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 are 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 an interesting term as this is what is frequently used by ENETS and NANETS in their technical documentation, sometimes to cover all Neuroendocrine types 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 ENETS, UKINETS 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 2011 Guidelines (Ramage, Caplin, Meyer, Grossman, et al).
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 guidance in 2017 WHO reinforces this statement to include endocrine organs, including the pancreas and adrenal glands.
The C Word (Carcinoid) – 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. ‘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.
The situation is made even more confusing by those who use the term “Carcinoid and Neuroendocrine Tumors” inferring that it is a separate disease from the widely accepted and correct term ‘Neuroendocrine Tumor’ or Neuroendocrine Neoplasm. A separate discussion on this subject can be found in this post here. I encourage you to stop using the term ‘Carcinoid’ which is just perpetuating the problem.
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 3 (High Grade) NET; and ‘Neuroendocrine Carcinoma’ for Grade 3 (High Grade) 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 article on Staging and Grading of NETs as this is also a poorly understood area.
Can some Tumours be Benign?
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). Adrenal and 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.
The ‘BUT’ is this – all WHO classification systems are based on the concept that all NETs have malignant potential. The WHO 2017 classification update confirmed this thinking by adding endocrine organs including the pancreas and adrenal glands.
Can Tumours be Malignant or become Malignant?
Using the definition above, if a tumour invades and destroy nearby tissue and spread to other parts of the body, then it’s malignant (i.e Cancer). 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. I do believe there are scenarios where NETs will be benign and probably never cause the person any real harm (e.g. many are found on autopsies). I suspect this is the same for many cancers. However, based on the above text and the stories of people who have presented for a second time but with metastatic disease, use of the word ‘benign’ is probably best used with great care.
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.
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 be interested in reading these associated posts:
Thanks for listening