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Why do I need to write about this?
I’ve been watching confusion surrounding symptomatic pancreatic NETs for years and it never ceases to amaze me that people automatically think “carcinoid syndrome”. Despite the fact that pancreatic NETs were never included in the category of “carcinoid tumours”; and despite the fact that there are at least 6 or 7 known pancreatic NET hormonal syndromes, this myth persists. Don’t misunderstand me though, a serotonin secreting pancreatic NET is possible, it’s just not nearly as common as it’s made out in patient groups and on some websites. It’s a highly unusual scenario.
Why is this a problem? A mixture of issues, including but not unlimited to; poor moderation in patient groups, websites out of date, doctors out of date, even the names of patient advocacy groups cause such confusion.
Many pancreatic NET patients claim carcinoid syndrome as they have diarrhea. But if you look at the symptoms of non-functional and functional pancreatic NETs, in addition to secondary issues, diarrhea comes up several times including but not limited to; non-functional pancreatic NET, and functional pancreatic NETs such as Gastrinoma, VIPoma and Somatostatinoma. Add confusion I see in patient groups between diarrhea and steatorrhea. Flushing already has several secondary causes outside of carcinoid syndrome – read more by clicking here.
Incidence of serotonin secretion in pancreatic neuroendocrine tumours
I wanted to confirm how uncommon this scenario was and found this study from some of the world’s most respected NET experts who work in one of the world’s most respected NET centres of excellence. This is backed up by another document referred below (Reference 1).
It’s known that serotonin can be elevated but not sufficiently to cause symptoms or carcinoid syndrome, which is true of many hormonal issues with most NETs. It’s also known that many cases of carcinoid syndrome do not manifest until there are liver metastases (or less common scenarios as described below).
According to Reference 1, Carcinoid syndrome occurs when biologically active amines and peptides enter the systemic circulation escaping the first-pass metabolism of the liver. Normally, these bioactive products are inactivated by the liver. However, in cases of neuroendocrine tumours with liver metastasis, either these bioactive products are directly released into the systemic circulation, or they escape inactivation due to deranged liver function. Less commonly, carcinoid syndrome can occur without liver metastasis in conditions like a primary gut tumour with extensive retroperitoneal nodal metastases, a bronchial or ovarian NET, where it’s possible for bioactive amines to be released directly into the systemic circulation.
According to Reference 2 below, elevated serotonin is possible in pancreatic NETs (7.8%) but only 0.8% were also diagnosed with carcinoid syndrome.
- Biochemical Testing in Neuroendocrine Tumors – Endocrinol Metab Clin North Am. 2017 Sep; 46(3): 669–677. Published online 2017 Jun 12. doi: 10.1016/j.ecl.2017.04.004 Vidya Aluri, MD, MS and Joseph S. Dillon, MB, BCh
- Incidence and prognostic value of serotonin secretion in pancreatic neuroendocrine tumours. Wouter T. Zandee, Roxanne C. van Adrichem, Kimberly Kamp, Richard A. Feelders, Marie-Louise F. van Velthuysen, Wouter W. de Herder First published: 02 May 2017 https://doi.org/10.1111/cen.13364
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