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For many years, I’ve been reading and blogging about Neuroendocrine Neoplasms, NENs for short. NEN is a relatively new term which came after my diagnosis. Nomenclature is still evolving and there is always something to learn. It’s also true to say the term ‘Neuroendocrine Neoplasms’ is the same as saying ‘Neuroendocrine Cancer’. These neoplasms are cancers that begin in specialised cells called ‘neuroendocrine cells’. Neuroendocrine cells have traits similar to those of nerve cells and hormone-producing cells, particularly the latter. In face one NET specialist said “While the name “neuroendocrine” implies that these tumors involve both nerve cells and hormones, they are mainly thought to come from endocrine cells. The “neuro-” is more of a quirk of history”.
The main reason the NEN term was introduced is so that the groups of well differentiated neuroendocrine tumours (NET) and poorly differentiated neuroendocrine carcinomas (NEC) could be described as a single entity, therefore encompassing the whole range of different neoplasms that made up this formerly rare disease. The division between NET and NEC has recently been described as a ‘dichotomy’, which means a division or contrast between two things that are or are represented as being opposed or entirely different. Within that contextual regrouping, the other major change is the addition of a high grade into the well differentiated sub-group (from 2017 onwards); at least for Gastroenteropancreatic (GEP) NENs. Also new in 2017, Mixed Neuroendocrine Non-Neuroendocrine Neoplasms (MINEN) adds another dimension to the riddle.
But there are further sub-groups, as even within these two high level groups, there are more riddles to be solved. I’ll cover some of those below under the ‘mystery’.
You can read more about this classification system by clicking here.
If you’ve solved the riddle above, let’s try to demystify the mystery! If you read any authoritative source on this cancer, it will normally begin with “Neuroendocrine Neoplasms (NENs) are heterogeneous tumours………….”. The term heterogeneous means diverse in character or content; or a structure with dissimilar components or elements.
This is not surprising as these tumours are found in Neuroendocrine cells throughout the vast majority of the human anatomy. The most important point to note is that other than cell of origin, nearly everything else is different. This can often lead to great confusion, even in other cancers as suddenly there is another type of cancer within the same organ but it is totally different one.
But that’s not all, If you drill further down into NENs, you find many examples of heterogeneity. For example, the most common primary locations of NECs and NETs can be very different. The propensity of a primary NET to metastasise is quite common in some primary types but much less common in others. NETs can vary from low stage low grade very indolent to high grade high stage very aggressive. And low grade with high stage is quite common. But many low grade NETs may still metastasise over a long period, i.e. there isn’t a direct correlation between grade and stage. In fact, in NENs, often grade is the differentiator rather than stage as is the case with many other cancer types. Given all of this, the prognostics can be quite different from person to person.
If you then drill further down into NETs, you’ll find added complications of ‘functional’ primary types producing hormonal syndromes, some of which can introduce some serious side effects including (but not limited to) diabetes and heart disease. But I’m now venturing into the ‘enigma’ section. Keep reading.
I can sense your eyes glazing over at this point. I don’t mean to be rude but I do believe one thing – if you don’t understand the heterogeneity of Neuroendocrine Neoplasms, it’s likely you don’t understand Neuroendocrine Neoplasms
There are many curious things about NENs. One of them is that certain types can very often exhibit one or more vague symptoms collectively known as a ‘syndrome’. I mentioned above that Neuroendocrine cells have traits similar to hormone-producing cells and it is the over-secretion from these cells which cause these syndromes. Syndrome is an apt word to describe these complications as the most general meaning in medical terms is a group of symptoms that together are characteristic of a specific disorder or disease”. When a syndrome is diagnosed, a person may be said to have a ‘functional’ tumour. Not everyone will be diagnosed as a functional case, most are not and it mostly involves metastatic cases. Each syndrome may involve different hormones.
The most important point here is that these symptoms can mimic very common day to day illnesses, making it difficult to diagnose until imaging tests are carried out. This can lead to diagnostic delays, missing the opportunity for curative scenarios in some and leading to worse prognostic outcomes.
NET hormonal syndromes are also a heterogenous collection but the main one people hear about is (so called) carcinoid syndrome, first described in 1954 by Thorson and co-workers, “……has the following features: malignant neuroendocrine tumour of the small intestine, normally with metastases to the liver, sometimes with valvular disease of the right side of the heart (pulmonary stenosis and tricuspid insufficiency without septal defects), peripheral vasomotor symptoms, bronchial constriction, and an unusual type of cyanosis”. One year later, Dr. William Bean gave the following colourful description of carcinoid syndrome, “This witch’s brew of unlikely signs and symptoms, intriguing to the most fastidious connoisseur of clinical esoterica—the skin underwent rapid and extreme changes resembling in clinical miniature the fecal phantasmagoria of the aurora borealis.”
Since these statements, we have learned that carcinoid syndrome can appear in other primary sites although less commonly than small intestine. We also know carcinoid syndrome is almost always in metastatic scenarios.
But know this, there are several other syndromes, particularly involving the pancreaticoduodenal region. They have different pathophysiology and hormone involvements. Some people and institutions only think of carcinoid syndrome. This can cause further delay.
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