Translate
Subscribe to Blog via Email
Ronny Allan
What are Rectal NENs
Rectal Neuroendocrine Neoplasms (NENs) (rNENs) account for approximately 1-2% of all primary cancers in the rectum. The other main cancer types found in the rectum are regular adenocarcinomas (the vast majority) and some other rare types including Gastrointestinal stromal tumors (GIST) and Lymphoma.
The vast majority of rNENs will be well differentiated, i.e. rectal Neuroendocrine Tumours (rNETs) and are mostly indolent tumours treated effectively with surgical procedures if less than 1cm in size. Above that size there are different scenarios.
Most will be found incidentally upon presentation of classic rectal symptoms or via colonoscopy screenings and faecal tests which lead to colonoscopy follow ups. They are typically diagnosed in older patients but the incidence in younger patients is on the increase, see author’s note below in epidemiology section.
Poorly differentiated rectal Neuroendocrine Carcinomas (rNEC) are much less common than well differentiated rNETs.
Mixed neuroendocrine-non-neuroendocrine neoplasms (MiNEN) are possible but ultra rare in that they are only found in case studies.
Anatomy
The rectum is the last several inches of the large intestine closest to the anus.
The location of the Rectum is shown below (this may be important for understanding radiology/pathology reports).
Epidemiology
Many sites combine colon and rectal NENs together for epidemiological data but rectal are more common than Colon NENs. Colorectal NECs are rare but Rectal NETs are said to account for up to 27% of all NETs and 20% of gastrointestinal NETs. Colon NETs, which are less frequent, account for only 9.6% of all NETs and 14.1% of gastrointestinal NETs,
The rectum appears to be the second most common place for NENs along the digestive tract and the third most common NEN behind lung and small intestine. But there is a global variation and the biggest NEN study, US SEER 2012, is now significantly out of date.
Poorly differentiated rectal Neuroendocrine Carcinomas (rNEC) are much less common than well differentiated rNETs. Only around 0.5% of all colorectal carcinomas are rNEC. Around 35% are Rectal located with a 40/60 split between small and large cell.
- Author’s note: The incidence of rNETs may be understated given the output from this study which claims that rNETs were common, representing approximately 4% to 20% of all colorectal and 8% to 34% of all rectal cancer cases, depending on age group and calendar year. Click here.
Syndromes and Rectal NENs
So called ‘carcinoid syndrome‘ is rare in rNENs, mostly due to the low stage and curative surgery approach. But any manifestation of carcinoid syndrome would be similar to small intestine NETs, e.g. almost always in metastatic cases.
Hereditary connections
There are no known hereditary connections with Rectal NENs. However, Familial adenomatous polyposis (FAP) is said to account for 1% of all cancers in the colon or rectum (given the numbers above, highly unlikely in rNENs).
Guidelines
There are numerous clinical practice guidelines on management of rNETs where management of these tumours is stratified according to risk of locoregional and distant metastasis. Most rNETs are less than 1cm (80-90%) and when there is negative margin, they will be removed with curative intent with no further surveillance necessary according to most guidelines. Tumours less than 1cm but without negative margins and tumours between 1 and 2cm may need more complex handling. Tumours over 2cm may need larger resections and longer surveillance periods. Metastatic cases would be considered alongside other metastatic NENs. The best diagrams explaining this are UKINETS and NCCN referenced below.
You may find slight differences in consensus of the various regional guidelines regarding tumours that measure 1-2 cm given the number of factors involved.
Guidelines for rNEC and MiNEN will be similar to other NEC and MiNEN.
Further Reading
- Review article: the investigation and management of rectal neuroendocrine tumours – PubMed (nih.gov)
- Diagnosis and Management of Rectal Neuroendocrine Tumors (NETs) – PMC (nih.gov)
- Pathology Outlines – Colorectal Neuroendocrine tumor
- Pathology Outlines – Staging colorectal Neuroendocrine tumor
- Comprehensive analysis of mutational and clinicopathologic characteristics of poorly differentiated colorectal neuroendocrine carcinomas | Scientific Reports (nature.com)
- Rectal Neuroendocrine Neoplasms: Why Is There a Global Variation? | SpringerLink
- NCCN Guidelines for Neuroendocrine Neoplasms (see page NET-4) – account login required.
- UKINETS Rectal NET Guidance
- ENETS Guidelines (needs ENETS membership or payment)
A Spotlight on Neuroendocrine Neoplasms – a series from Ronny Allan
Disclaimer
I am not a doctor or any form of medical professional, practitioner or counsellor. None of the information on my website, or linked to my website(s), or conveyed by me on any social media or presentation, should be interpreted as medical advice given or advised by me.
Neither should any post or comment made by a follower or member of my private group be assumed to be medical advice, even if that person is a healthcare professional.
Please also note that mention of a clinical service, trial/study or therapy does not constitute an endorsement of that service, trial/study or therapy by Ronny Allan, the information is provided for education and awareness purposes and/or related to Ronny Allan’s own patient experience. This element of the disclaimer includes any complementary medicine, non-prescription over the counter drugs and supplements such as vitamins and minerals.
Top 10 Posts & Pages in the last 48 hours (auto updates) (Click the titles to read them)
Thanks for reading.
Personal Facebook. Like this page please.
Blog Facebook. Like this page please.
Awareness Facebook Like this page please.
Sign up for my newsletters – Click Here
My Diagnosis and Treatment History
Check out my online presentations
Check out my WEGO Health Awards
Check out my Glossary of Terms – click here
Please Share this post for Neuroendocrine Cancer awareness and to help another patient
Neuroendocrine Cancer: Question, Clarify, Confirm
One of the many observations I make in my private Neuroendocrine Cancer Facebook group is the misunderstandings caused by the use of non-standard terminology combined
Clinical Trial – Lutathera NETTER-2 Important Update
UPDATE – Sep 25th, 2023 – Novartis radioligand therapy Lutathera® demonstrated statistically significant and clinically meaningful progression-free survival in first line advanced gastroenteropancreatic neuroendocrine tumors
Lanreotide: Ipsen injection devices vs generic injection devices
Whenever I get a chance to talk to a pharma involved in somatostatin analogue injection devices, I tell them one very important thing …… “To
Cancer doesn’t take holidays (but I do)
Glen Etive Scotland in 2018 After diagnosis in July 2010, with the exception of a planned holiday to Turkey prior to my ‘big surgery’, holidays
Update from Ronny Allan: No evidence of progressive disease at any site
Update August 2023. Latest CT surveillance scan reports “No evidence of progressive disease at any site”. Very pleased! With incurable but treatable cancers such as
Exercise is Medicine
Exercise is medicine. Clearly I need to be careful with that statement given my aversion for cancer myths. However, those who know me will totally
Jimmy Buffett 1946-2023 – Neuroendocrine Carcinoma (Merkel Cell Carcinoma)
US singer-songwriter Jimmy Buffett, best known for his 1970’s hit Margaritaville, has died aged 76. “Jimmy passed away peacefully on the night of September 1
Passive patient or active advocate?
I’ve been researching Neuroendocrine Cancer for some time now. Why do I do this? Whilst I have a great medical team, I’d also like to
Childhood Cancer Awareness Month – Neuroendocrine Cancer (featuring Elizabeth)
September is Childhood Cancer Awareness Month! The newspapers and social media will no doubt be featuring many childhood cancer articles. You may not see one
Subscribe to Blog via Email
A cup of tea
I would also mention those who contributed to my “Tea Fund” which resides on PayPal. You don’t need a PayPal account as you can select a card but don’t forget to select the number of units first (i.e. 1 = £4, 2 = £8, 3 = £12, and so on), plus further on, tick a button to NOT create a PayPal account if you don’t need one. Clearly, if you have a PayPal account, the process is much simpler
Through your generosity, I am able to keep my sites running and provide various services for you. I have some ideas for 2023 but they are not detailed enough to make announcements yet.
This screenshot is from every single post on my website and depending on which machine you are using, it will either be top right of the post or at the bottom (my posts are often long, so scroll down!)
