It has long been observed that certain Neuroendocrine Tumours (NETs) are often associated with the development of fibrosis, both local and distant. Fibrotic complications, such as Hedinger Syndrome (so-called Carcinoid Heart Disease), mesenteric and retroperitoneal fibrosis, may lead to considerable morbidity. We talk a lot about CHD but mesenteric fibrosis is actually more common. According to a paper (abstract linked below) by Professor Martyn Caplin (et al), “it often has a characteristic appearance of a mesenteric mass with linear soft tissue opacities radiating outward in a “wheel spoke” pattern associated with distortion of the surrounding tissues” (see graphic below). Another area that can be affected by fibrosis is the retroperitoneal region, actually very close to the mesentery. The medical phenomena appears to be associated with small intestine NET (SI NET) patients. Often labelled ‘Desmoplasia’, it is easily spotted on CT scans and is one of the unusual features of NETs vs other types of cancer.
The mesentery and retroperitoneum are complex to describe but think of the mesentery as something holding the small intestine together with all its folds and the retroperitoneum describes the part of the abdomen that is generally closer to your backbone than to your belly button, i.e. behind the intestines.
What causes it, what problems does it cause and how can it be treated?
As with Hedinger Syndrome, which mostly causes right-sided fibrosis in the heart, mesenteric and peritoneal fibrosis is thought to be caused by the excess secretion of serotonin from NETs. I say ‘thought’ but no-one really knows for sure. There’s a few quite recent studies on the subject which I’ll provide abstracts here.
Uppsala Hospital Sweden. In one study entitled “Clinical signs of fibrosis in small intestinal neuroendocrine tumours” first published in November 2016 by Uppsala Hospital Sweden, it said that it was caused by serotonin and other cytokines released from tumour cells and which may induce fibrosis, leading to carcinoid heart disease and abdominal fibrotic reactions. A cohort study of patients with SI NETs diagnosed between 1985 and 2015 was carried out – a total of 824 patients. Clinically significant abdominal signs and symptoms of fibrosis occurred in 36 patients. Of these, 20 had critically symptomatic central mesenteric fibrosis causing obstruction of mesenteric vessels, and 16 had retroperitoneal fibrosis causing obstructive uropathy with hydronephrosis (the swelling of a kidney due to a build-up of urine). Extensive fibrosis causing mesenteric vessel obstruction and/or obstructive uropathy was more often associated with symptomatic and advanced disease encompassing lymph node metastases in the mesenteric root, para‐aortic lymph node metastases, as well as liver metastases and peritoneal carcinomatosis. Palliative intervention in terms of superior mesenteric vein stenting or resection of central mesenteric metastases and/or percutaneous nephrostomy and J stent treatment was beneficial in the majority of the patients. They concluded by saying that extensive abdominal fibrosis associated with clinically significant symptoms of intestinal ischaemia and/or obstructive uropathy was linked to advanced disease in patients with SI NETs. Prompt recognition and minimally invasive intervention was effective in disease palliation.
Royal Free Hospital. In another fairly recent paper entitled “Neuroendocrine tumors and fibrosis: An unsolved mystery?”, published by Professor Martyn Caplin of the Royal Free (and others), where this issue is discussed alongside the role of serotonin, growth factors, and other peptides in the development of NET related fibrotic reactions. They also suggested serotonin as the culprit in both CHD fibrosis and in mesenteric/retroperitoneum and expressed many of the factors above. This study suggested that up to 50% of SI NET patients may be involved but looking at both reports together indicates that the first study above only isolated clinically significant cases whereas Royal Free looked for signs in all cases.
Another recent paper (also a paid subscription) from Royal Free (Caplin et al) indicated that the severity of mesenteric desmoplasia did not seem to demonstrate a statistically significant effect on overall survival or long-term outcome (taken from a study of 147 patients at Royal Free London). Sounds like good news.
I do not have access to all the texts above, only the abstracts which I’ve linked (all only available from paid subscriptions).
What happened to me?
Since I was diagnosed in 2010, I’ve always known I’ve had a fibrosis issue in the retroperitoneal area, as it was actually identified on my very first CT Scan, which triggered my diagnosis. Here’s how the radiologist described it – “There is a rind of abnormal tissue surrounding the aorta extending distally from below the renal vessels. This measures up to 15mm in thickness”. He went on to describe that “almost certainly malignant”. The second and third scans would go on to describe as “retroperitoneal fibrosis” and “a plaque like substance”. Interestingly the fibrosis itself does not appear to ‘light up’ on nuclear scans indicating it was not cancerous (see below).
I really didn’t know what to make of this issue at diagnosis, although I did know the aorta was pretty important. Fortunately I had a surgeon who had operated on many NET patients and has seen this issue before. After my first surgery, he described it as a “dense fibrotic retroperitoneal reaction encircling his aorta and cava (inferior vena cava (IVC))”. My surgeon was known for difficult and extreme surgery, so as part of the removal of my primary, he also spent 3 hours dissecting out the retroperitoneal fibrosis surrounding these important blood vessels and managed 270 degree clearance. The remnant still shows on CT scans. Some of the removed tissue was tested and found to be benign, showing only florid inflammation and fibrosis (thankfully). That said, the abstract papers above has led me to believe that my retroperitoneal fibrosis is clinically significant.
These issues need to be identified early on in diagnostics, preventative treatment considered and then monitored going forward. Potential complications may include (but not be limited to) bowel and blood vessel obstructions. Retroperitoneal fibrosis also needs to be monitored as potential complications may include (but not be limited to) obstructive uropathy.
For those worried about this issue, please note that when you look at the statistics from Uppsala, only 4.5% of cases are classed as clinically significant and with the retroperitoneal area, the figure reduces to 2%.
Recent Ga68 PET confirms active lymph nodes in the retroperitoneal area that might be contributing to continued or new fibrosis growth. Read more by clicking here.
Thanks for reading