Neuroendocrine Neoplasms – High grade



High Grade – the forgotten patient group?

When reading articles in the mainstream media, found in medical publications; and even listening to doctors speak about my disease, it’s clear that the focus is on the term “Neuroendocrine Tumours” or NET for short.  Many websites of advocate foundation organisations and specialist scientific organisations, all still use the term “NET” in their naming.  I too am guilty of having a large Facebook site falling into this category.  It’s little wonder that those with high grade disease can often feel like the forgotten patient group.  Clearly all the aforementioned organisations support all patients regardless of grade, but it’s true to say that the naming and general use of terminology continues to fall behind. It’s also true that the term NET remains applicable to the majority of patients and that many use it as a convenience when they actually mean all types including Neuroendocrine Carcinoma. Nonetheless, context remains an important part of overall understanding and inclusivity – words and acronyms matter.

However, High grade or Grade 3 is no longer just Neuroendocrine Carcinoma (NEC).  Things have changed since 2017.

What are Neuroendocrine Neoplasms?

Neuroendocrine neoplasms (NENs) are without doubt a heterogeneous (i.e. diverse) bunch of tumours with a common phenotype (i.e. the physical appearance or biochemical characteristic).  However, there are two fundamentally different groups of NENs: well-differentiated, low-proliferating NENs, called neuroendocrine tumours (NETs), and poorly differentiated, highly proliferating NENs, called neuroendocrine carcinomas (NECs).  The difference between well and poorly differentiated has been described as a ‘dichotomy’, most likely due to the origin from different neuroendocrine progenitor cells (i.e. source cells). Should the term Neuroendocrine Neoplasm be used more?  Yes, probably. But should we perhaps also ask if ENETS and NANETS will change their names to ENENS and NANENS?

This revised classification is not recent as many are currently suggesting.  These changes were covered in my Staging and Grading article produced in early 2017 and confirmed Neuroendocrine Neoplasms (or NENs) was the overarching term for all types of neuroendocrine disease.  See graphic below.

Traditionally, any proliferation score over 20% on the Ki-67 proliferation index (or over 20 mitoses/10 HPF on the Mitotic Index) would have been deemed a Neuroendocrine Carcinoma.  However, in the pancreas, NETs and NECs may overlap in their proliferation index, making the distinction between them difficult and leading to treatment uncertainties.

In 2017, the Endocrine ‘Blue Book’ of cancer classification systems introduced a new pancreatic NET category based on a Grade 3 tumour which is well differentiated (i.e. cancer cells look more like normal cells and tend to grow and spread more slowly).  While all classifications for all NENs recognise the existence of the two major groups (NET and NEC), there are proposals to develop common NEN classification across all the ‘Blue Books’ and future versions will reflect these changes. The most interesting change will be in the Lung classification because high grade NENs can be small cell or large cell and it’s probably the most controversial grouping.

Interestingly, ENETS guidelines already use the term across the board in their 2016 series (i.e. in advance of the 2017 changes).  These changes are part influenced by the results of the NORDIC NEC study which showed that although patients with a Ki67 <55% were less responsive to platinum-based chemotherapy (i.e. drug names ending in ‘platin’ such as Cisplatin, Carboplatin, Oxaliplatin), they had a longer survival, and concluded that not all NEC should be considered as one single disease entity.  Also worth noting that the NORDIC NEC study covered many different areas of the anatomy, not just the pancreas. Some of the rationale for the division of grade 3 into well differentiated NETs and poorly differentiated carcinomas is that some grade 3 tumours which are classified into this category according to the Ki67 index percentage, have been recognised to behave more like grade 2 NETs rather than aggressive carcinomas. The inference is that there could be treatment and prognostic significance if a patient is a Grade 3 NET.

MANEC vs MiNEN

Added for completeness.  This mixed and rare neoplasm type has traditionally been related to NEC but in 2017 the nomenclature change to a new term was necessary to reflect the fact that some of the tumours involved were not carcinomas or adenocarcinomas but rather were well differentiated tumours or even adenomas (i.e. benign). Previously known as Mixed AdenoNeuroendocrine Carcinoma (MANEC), they were renamed to Mixed Neuroendocrine Non-Neuroendocrine Neoplasms (MiNEN).

MiNEN are neoplasms with two distinct neuroendocrine and non-neuroendocrine cell populations. They can be morphologically classified into three entities: collision, composite, and amphicrine MiNEN. Currently, both components composing a MiNEN must represent at least 30% of the whole tumour.  Diagnosis of MiNEN is usually facilitated by the presence of at least one well-differentiated component which may be the Neuroendocrine or Non-Neuroendocrine component. However, the two components may be difficult to identify with conventional morphological techniques, particularly when they are poorly differentiated, and their identification may require additional immunohistochemical techniques. MiNEN usually originate from organs that contain neuroendocrine cells and in which “classical” NENs are known to develop, such as pancreas, appendix, colon, and to a lesser degree small intestine. Other locations in my source document includes Oesophagus, Stomach, Bilary Tract and Gallbladder, Duodenum and Ampulla of Vater and Rectum.

NEC vs NET

Having researched widely, I believe there are 8 key differences between NET and NEC:

      1. Grade – NEC is only Grade 3, NETs can be Grade 1, 2 or 3.
      2. Differentiation – all NETs are well differentiated, NECs are poorly differentiated.  Important difference at Grade 3.
      3. Aggressiveness – Most NETs tend to be indolent or slow growing while NECs tend to be aggressive and faster growing. However, Ki67 and/or mitotic count is an aggressiveness measurement tool.  Genetic profiles can also be a guide but this is beyond the purposes of this article but may be explored in subsequent parts.  It follows that NECs normally have a worse prognosis in comparison to NETs.
      4. Hormone Secretion – NETs can produce peptide hormones that may be associated with hormonal syndromes.  NECs usually fail to express hormones or produce hormonal syndromes.
      5. Somatostatin Receptors – A NET is much more likely to express somatostatin receptors which can influence treatments such as somatostatin analogues and peptide receptor radiotherapy (PRRT)
      6. Hereditary Syndromes – NETs are much more likely to be associated with hereditary syndromes such as Multiple Endocrine Neoplasia (MEN).
      7. Platinum Based Chemotherapy – NETs are less likely to show a good response to platinum based chemotherapy which can often be the first line treatment for NEC.
      8. Primary Locations – can be vastly different in terms of commonality and therefore provide clues to investigators. Common locations for NEC include: Lung, Esophagus, Colon, Urogential Organs and Skin –  with the exception of Lung, these are very rare locations in NETs.  Conversely, rare/very rare locations for NEC but common in NET include: Rectal, Small Intestine, Appendix, Stomach, Pancreas.

Summary

I intend to cover more on Grade 3 tumours going forward and a ‘Part 2’ article will follow covering treatment differences, genetic profiles and unmet needs.

In addition to my own knowledge gained over the years of researching and writing, the following resources were key in establishing the facts used in compiling this article:

1. Sorbye H, Welin S, Langer SW, Vestermark LW, Holt N, Osterlund P, et al: Predictive and prognostic factors for treatment and survival
in 305 patients with advanced gastrointestinal neuroendocrine carcinoma (WHO G3): the NORDIC NEC study. Ann Oncol 2013; 24: 152–160

2. de Mestier L, Cros J, Neuzillet C, Hentic O, Egal A, Muller N, Bouché O, Cadiot G, Ruszniewski P, Couvelard A, Hammel P: Digestive System Mixed Neuroendocrine-Non-Neuroendocrine Neoplasms. Neuroendocrinology 2017;105:412-425. doi: 10.1159/000475527

3. Koppel G: Neuroendocrine Neoplasms: Dichotomy, Origin and Classifications. Visc Med 2017;33:324-330. doi: 10.1159/000481390

4. Rindi G, Klimstra DS, Abedi-Ardekani B, et al. A common classification framework for neuroendocrine neoplasms: an International Agency for Research on Cancer (IARC) and World Health Organization (WHO) expert consensus proposal. Mod Pathol. 2018;31(12):1770–1786. doi:10.1038/s41379-018-0110-y

Thanks for reading

Ronny

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Neuroendocrine Neoplasms – Grade and Stage (incorporating WHO 2017 changes)

 

Grades of Neuroendocrine Tumour

One of the most discussed and sometimes confusing subjects on forums is the staging and grading of Neuroendocrine Neoplasms (NENs). Mixing them up is a common error and so it’s important to understand the difference despite the apparent complexity. If I was to make a list of questions for my specialist/Oncologist at diagnosis, it would include “What is the stage, grade and differentiation of my cancer”.  To enable me to synchronise with the documented guidance, I’m going to use the following WHO 2017 approved terms in this post:

  • Neuroendocrine Neoplasm (NEN) – all types of Neuroendocrine tumour of whatever grade (please note Neoplasm is another word for tumour)
  • Neuroendocrine Tumour (NET) – all well-differentiated tumours (an explanation of differentiation will be provided below)
  • Neuroendocrine Carcinoma (NEC) – all poorly differentiated tumours

NEN Breakdown

Stage vs Grade

In the most basic of terms, stage is the spread or extent of cancer and grade is the aggressiveness of cancer. They are totally different things and an understanding of both is important as they are critical to predict outcome (to a certain extent) and guide therapy. There is no correlation between the two, you can have the lowest grade with the highest stage (actually very common with NETs).

As patients, we deal with many medical specialists during diagnosis and subsequent treatment.  However, we rarely meet the pathologist who plays a critical role in the outcome. Precise diagnosis is what drives patient decisions and treatment. If the pathology is wrong, everything that follows could be incorrect as well.  It’s a very important area.

Grading (aggressiveness)

Grading and Ki67

Antigen KI-67 is a nuclear protein that is associated with and may be necessary for cellular proliferation.  Ki-67 is therefore an excellent marker to determine the growth fraction of a given cell population. The fraction of Ki-67-positive tumour cells (the Ki-67 labeling index) is often correlated with the clinical course of cancer.

Pathologists normally need to count about a thousand cells in order to determine the percentage of cells that are Ki67 positive – thus why you see Ki67 expressed as a percentage. 0% is the lowest, 100% is the highest. Often, they add greater or less than signs depending on the sample involved, i.e. >5% or <5%. There are other measurement systems in place, mainly Mitotic Count.

The ranges for Neuroendocrine Neoplasms (NENs) are divided in to 3 Grades depending what range the Ki67 number lands in. With NENs, the differentiation (well or poorly) is almost as important at grade 3 (high grade).  Grades 1 and 2 are by default well differentiated NETs).

Why is differentiation important?

To fully understand grading, you also need to understand the concept of ‘differentiation’.  In the most basic of terms, ‘differentiation’ refers to the extent to which the cancerous cells resemble their non-cancerous counterparts.  This is an important point for NETs because many low-grade tumour cells can look very similar to normal cells. The differentiation of a NET has an impact on both prognostics and treatment regimes.

NENs fall into one of three grades based on their differentiation and their proliferative rate. The proliferative rate is measured mainly using two methods known as Miotic Count and Ki-67 index, the latter seems to be more frequently used (but see below for Lung NETs). The Ki-67 index can usually be determined, even in cases of small biopsies but Mitotic rate counting requires a moderate amount of tumour tissue (at least 50 HPFs or 10 mm) and may not be feasible for small biopsies.  The Miotic Count method may be preferred or used in addition to Ki-67 for certain Lung NET scenarios as it is said to be more helpful in distinguishing atypical from typical NET (what some might ‘old fashionably’ and incorrectly refer to as Lung Carcinoid tumours), and for small and large cell lung Neuroendocrine Carcinomas (NEC).

Some of you may have heard the term ‘moderately differentiated’ which tended to align with an intermediate grade or Grade 2. However, please note that the term moderately differentiated as a classification was phased out in 2010 by WHO reducing from 3 differentiation levels to 2.  Grade 2 is also defined as well differentiated but based on different proliferative rate (see table). High grade was normally referred to as Neuroendocrine Carcinoma indicating it is a faster growing and more aggressive cancer. However, see below for an important change to high grade classification.

Grading – Key WHO 2017 Changes

WHO Classifications of Cancer are published in something known in medical world as “The Blue Book”.  For NETs, the 2017 version comprises only the “WHO Classification of Tumours of Endocrine Organs”.  Technically this would preclude the digestive system and lung NETs but the leading NET pathologists have submitted a recommendation to normalise all NET Blue Books along the same classification scheme.  Worth also noting that the latest ENETS Guidelines are already using the new grading terms.  Many sites remain out of date so be careful where you look.

Misc Grading Issues

The proliferative rate can be diverse in NENs, so sampling issues can limit the accuracy of grading. More substantial samples of tumour are therefore preferable for grading thus why the Ki-67 index is preferred for biopsies where large amounts of tissue may not be available. The distinction of low-grade from intermediate grade can be challenging when using small samples. A couple of interesting observations about NET grading which I spotted during my research and ‘forum watching’.  You can have multiple primary tumours and these might have different Ki-67 scores.  Additionally, on larger tumours, Ki-67 scores can be different on different parts of the tumour.  And something I know from my own experience, secondary tumours can have different Ki-67 scores than primary – even a different grade.  In my own case, my liver secondary tumours were graded higher than my primary which according to my surgeon is in keeping with a clone of the disease having become more aggressive over time.  Royal Free Hospital NET Centre indicates a person’s grade should be taken from the highest biopsy grade taken. This is a fairly complex area but a recent study published by the US National Institute of Health and many anecdotal comments made by NET specialists indicates that is a fairly common scenario.

 

Summary of Key Changes

The 2017 World Health Organisation (WHO) classification sub-divided Grade 3 into two new entities: a well differentiated high-grade NET and a poorly differentiated high-grade NEC.  There may also be a cut-off point in proliferative rate (i.e. Ki-67) between NET and NEC in relation to potential treatment strategies (55% is mentioned for pNETs but I’m currently investigating). Physicians don’t really have much data to support specific guidelines for treatment so all cases will be personalised.

The Grade 1 to 2 Ki-67 cut-off is changed from 2 to < 3 for clarification purposes.  There was some discussion as to whether it should be <5 but this was not accepted.

Well differentiated High Grade NETs are now recognised.  These are known as a NET rather than a NEC.  Both Grade 3 (NET) and Grade 3 (NEC) have the same biopsy marker cut-offs as per the leading slide but it is thought that a threshold reading of 55% could have some influence on the treatment regime. For example, a well differentiated tumour with a Ki67 of less than 55% might benefit from the same treatment given to Grade 1 or 2 patients, whereas a well differentiated tumour with a Ki67 of more than 55% might benefit from the same treatment given to poorly differentiated NEC. Only a guideline and I suspect this is like many things in NENs, very individual, relies on many factors, so your specialist will drive this accordingly.  You may see these 2 grades listed as Grade 3a for NET and Grade 3b for NEC.

Previously, Pheochromocytoma did not have an official grading regime, i.e. they were just benign or malignant.  Now they are using the same grading system as above.  I’m assuming this is the same for Paraganglioma and I will confirm in due course.  This is an excellent change and a continuation from the WHO 2010 classification where there was great emphasis away from a benign/malignant classification to formal grade levels on the basis that all NETs have malignant potential.

It also introduced a change to the naming of mixed cell tumours from Mixed AdenoNeuroendocrine Carcinoma (MANEC) to Mixed Neuroendocrine Non-Neuroendocrine Neoplasms (MiNEN).  A full explanation of MiNEN will follow but I would suggest the use of the term ‘Neoplasm’ has been chosen rather than ‘Carcinoma’ is because these neoplasms can be well or poorly differentiated.

It’s not possible at this time to acquire copies of the official output but I will keep this blog live.

The source material for the 2017 version of this article.

From leading Pathologist Dr Anthony Gill – Remember this is based on Endocrine Organs only but it will eventually apply to all.   I am awaiting access to free documentation to update this article further – only ones I can currently find are not free!

 

Staging (spread)

Staging is the extent or spread of disease.  Most types of cancer have 4 stages, numbered from 1 to 4 indicating a rising spread as the number is bigger. Often doctors write the stage down in Roman numerals, perhaps this is to stop any confusion between standard numbers used for Grades? So you may see stages written as I, II, III and IV.  In addition to this standard method, there is also an agreed model known as TNM (Primary Tumour, Regional Node, Distant Metastasis) which is essentially a more detailed staging definition when combined with the Stage 1-4 model.  Please note with TNM models, there could be different stage descriptions depending on the location of the primary tumour and similarly different TNM models for different tumour locations.

WHO 2017 changes

WHO 2017 has recommended enhancements to the TNM system mainly the use of additional suffixes indicating the extent of lymph node involvement. Details to follow when I can free access.

The following example shows the stage descriptions for a NET of the small intestine (the others are similar but worded accordingly for that part of the anatomy):

Stage I tumour is less than 1 cm in size and has not spread to the lymph nodes or other parts of the body.

Stage II tumour is greater than 1 cm in size and has started to spread beyond the original location, but has not spread to the lymph nodes or other parts of the body.

Stage III is any size tumour that has spread to nearby areas of the body and also to at least one lymph node.

Stage IV is any size tumour that has spread to one or more lymph nodes and has also spread to other, more distant areas of the body (such as the liver).

It’s also worth pointing out that Stage IV does not necessarily mean a cancer is more dangerous than other cancers of lesser stages.  This is an important point for NETs where Stage 4 can be matched up with a low-grade tumour i.e. Stage 4 for lower grade NETs is very often not the ‘red flag’ it is for other more aggressive cancers.  For example, doctors may surgically remove a Stage IV NET, while surgery might not help a patient with a cancer of a higher grade at such a late stage.

Notes:

  • Sometimes doctors use the letters to further divide the number categories – for example, stage 2A or stage 3B.  This is normally to clarify or provide more detail of the primary tumour size/invasion in conjunction with the TNM model.
  • You may also see something called Stage 0 which is for ‘Carcinoma in situ’. It means that there is a group of abnormal cells in an area of the body. However, the number of abnormal cells is too small to form a tumour and may, therefore, be currently classed as benign.  The World Health Organisation (WHO) system does not appear to recognise Stage 0 for NETs.

The most generic model for TNM staging is below but please note this could be adjusted for particular types of NET.

Primary Tumor (T)
TX: Primary tumor cannot be evaluated
T0: No evidence of primary tumour
Tis: in situ (abnormal cells are present but have not spread to neighbouring tissue; although not cancer, in situ may become cancer and is sometimes called preinvasive cancer)

T1, T2, T3 and T4 is a measure of the size of, and/or invasion/penetration by, the primary tumour and the wording varies between different NET sites. e.g. for a small intestinal NET:

T1 tumour invades mucosa or submucosa and size <=1 cm

T2 tumour invades muscularis propria or size >1 cm

T3 tumour invades subserosa

T4 tumour invades the visceral peritoneum (serosa)/other organs

For any T add (m) for multiple tumours

Regional Lymph Nodes (N)
NX: Regional lymph nodes cannot be evaluated
N0: No regional lymph node involvement
N1: regional lymph node metastasis

Distant Metastasis (M)
MX: Distant metastasis cannot be evaluated
M0: No distant metastasis
M1: Distant metastasis is present

You may occasionally see TNM staging be prefixed by lower case letters.  The most commonly used prefix is ‘p’ simply meaning the grading has been confirmed by pathology.  e.g. pT4 N1 M1

Specialists can combine the Stage to create a TNM – for example:

This slide will be updated when I get access to WHO 2017 or updated AJCC pubication.

Summary

A complex area and I hope I have condensed it sufficiently for you to understand enough for your purposes.  Despite looking very scientific, it is not an exact science. There are many variables as there always are with Neuroendocrine disease.  NENs can be very challenging for a pathologist even an experienced one who may not have encountered NENs before.  However, it is an extremely important part of initial diagnosis and also when needed during surveillance.  It is a vital tool used by Multidisciplinary Teams (MDT) in treatment plans and for prognostic purposes.  If you need to learn further, I recommend this document:

If you are interested in this subject and have one hour to spare, there is a great video here from LACNETS worth watching.

Finally – always make sure you get your pathology results at diagnosis and following any subsequent sampling.

You may benefit from reading these associated posts:

Benign vs Malignant

Incurable vs Terminal

Carcinoid vs Neuroendocrine

10 Questions for your doctor

Looking for a needle in a haystack

Thanks for reading

Ronny

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