Genetics and Neuroendocrine Tumors


In my article ‘Ever wonder what caused your NET’, I concluded that currently, the only known scientifically explained causes for NETs were hereditary/genetic in nature.  This is mostly associated with those who have MEN syndromes (yes, they are a syndrome not a type of tumour) and a few other less common types of NET including Pheochomocytoma/Paraganglioma (Pheo/Para) and Medullary Thyroid Carcinoma (MTC) (the familial version of MTC is often referred to as FMTC). However, please note this does not mean that all those diagnosed with pancreatic, parathyroid, pituarity, Pheo/Para and MTC tumours, will have any hereditary or genetic conditions, many will simply be sporadic tumors.

In recent years, it has become increasingly apparent that a number of Neuroendocrine tumours arise as a result of germline genetic mutations and are inherited in an autosomal dominant pattern. The number of genes implicated is increasing.

Apparently, 5-10% of Gastroenteropancreatic NETs (GEP NETs) are estimated to have a hereditary background. Hereditary syndromes associated with these include Multiple Endocrine Neoplasia (MEN), Von Hippel Lindau (VHL), Neurofibromatosis Type 1 (NF1), Tuberous Sclerosis (TS) and others. People who have a genetic condition may present with the tumors (perhaps along with an associated functional hormone syndrome) and so the genetic condition if there is one, may not be known at this point.

genetics locations
Overview of genes with recurrent mutations in NETs and their distribution accordingly to anatomical location. Please note the percentages on the above diagram may differ depending on where you look).  
Citation: European Journal of Endocrinology 174, 6; 10.1530/EJE-15-0972

How will I know if I am affected? 

Some people do worry about this, often because of what they find on the internet including inside patient forums.  I suspect some people already know via family connections and as an example (there are many), I guess if you have 2 tumors found in (say) parathyroid and pancreas, it should at least raise a suspicion for MEN1 and be investigated.

Many people say how do I know, how do I check and this is obviously a delicate subject.  Of course, your first port of call should be your NET specialist if you suspect or know of any connection.

Thus why I was interested in a paper published in Springer Link – titled “When should genetic testing be performed in patients with neuroendocrine tumours.”  When reading, you’ll find it’s actually much more than that! Check it out here:

Crossref DOI link: https://doi.org/10.1007/s11154-017-9430-3

In this review, the authors examined the features which may lead a clinician to suspect that a patient may have an inherited cause of a NET and they outlined which underlying conditions should be suspected. They also discussed what type of screening may be appropriate in a variety of situations. If there is a way to identify which patients are likely to have a germline mutation, this would enable clinicians to counsel patients adequately about their future disease risk, and allows for earlier detection of at-risk patients through family screening. There’s a couple of minor errors in the text but I’ve contacted the authors who also agreed they should have included the pituitary.

The authors focused on presentations of NETs of the gastrointestinal system, chromaffin cell tumours (Pheochromocytoma and Paraganglioma) and Medullary Thyroid Carcinoma. Pituitary tumors (normally associated with MEN1), were not considered in scope for the review.  Interesting thought, the review includes news of a move by endocrinologists to reclassify ‘Pituitary Adenomas’ as Pituitary NETs (PitNETs). Read the abstract here.  This would appear to be in line with a gradual shift from the benign nomenclature associated with certain NETs to the ‘malignant’ potential of these type of tumors.  The abbreviation is also in line with others, e.g. pNET, SiNET, etc.  A useful reminder that we must stop using the term ‘Carcinoid‘ as this is regressing this extremely useful initiative to highlight the malignant potential of all NETs.

There also appears to be some linkage to the study looking at the possibility of familial Small Intestine NETs (SiNETs).  You can read more about a US registered trial here (with apologies for use of the now defunct term ‘Carcinoid‘).

This is a complex subject and the text above is very basic. If you wish to dig further, the quoted reference is a good read.  Just to emphasise, it’s aim is to provide advice about when to recommend genetic testing for NETs, and in doing so provides some useful reference information.  Please also note they are finding new genetic links all the time so there could be some omissions of recently discovered genes but the article remains good enough as a primer on the subject.  It’s broken down into 4 distinct tumor groupings:

1.  Gastroenteropancreatic (GEP NETs)

2.  Bronchial/Thymic NETs

3.  Pheochromocytoma/Paraganglioma  The familial connection with Pheo/Para is complex. Up to 13 genes have been identified including NF1, RET, VHL, SDHA, SDHB, SDHC, SDHD, SDHAF2(SDH5), TMEM127, MAXm EPAS1, FH, MDH2.  Read more here (recent update)The NIH also have a useful section – click here.

4.  Medullary Thyroid Carcinoma

You may also find this article from the National Cancer Institute very useful.  It has a wider scope but a different aim. Genetics of Endocrine and Neuroendocrine Neoplasias (PDQ®)–Health Professional Version”

I also noted the UKINETS Guidelines for NETs has a section on genetics and includes something called Carney Complex.

Thanks for reading

Ronny

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10 thoughts on “Genetics and Neuroendocrine Tumors

  • Mark

    Excellent article Ronny! A friend of mine gave me a tour of the Genome Campus near Cambridge last week. I was blown away by their work, collaboration, and goals. I find it amazing you can already sequence a gene for half the cost of a MRI. And, handheld scanners are being fielded.

    Its a heck of a shot of hope! Especially for developing personalised drugs/therapies.

    This is actionable genetic code. With artificial intelligence they should be able to speed things up vs the old clinical trial system (of averages).

    If treatments like PRRT can hold us for several years, our future looks bright. Because, future therapies (& appraisals) may be amazingly personal.

    Loads of issues here for patients to be part of the work to keep things fair.

    Exciting times Ronny!

    Cheers,

    Mark

  • Kim

    I have 2 pnets. The surgeon discovered mine whilst I am on a research programme he is heading up- Europac.
    He believes I am probably predisposed yo Pancreatic Adenocarcinoma as 2 immediate family
    Members succumbed to this. And now thinks there maybe a link between that and my pNets and is now going to investigate possible MEN1.
    There is much being learned about NETs as a whole, however so much more still to learn.
    I feel very unlucky to have pNets in view of my family history, however equally lucky to have been diagnosed so early.

  • I’m so interested in this topic. Until this year, every doctor said it was a mutation, but now, signs are pointing to genetics and I have a family member who’s passing is very suspect. Looking forward to more research on this. Thanks for starting the conversation.

  • I would like to add the SDHx mutations (SDHA, SDHB, SDHC, and SDHD) that can present as paras/pheos/gists/RCC. My father died of paras. His sister died of paras. I have only had Gist tumors (and lots of them). The reason it is important to know if you have a mutation is because your children could inherit your disease or another disease associated with the germline mutation. I put up my own website because SDHB Deficient Gists are such a small subset but we all have a extended family history of cancer and are often miss diagnosised by our GP and surgeons (benign) when it is most likely NOT benign. http://www.SDHcancer.org

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