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Inflammatory bowel disease and coexistence of neuroendocrine neoplasms: A review of the literature.

e16206 Background: Inflammatory bowel disease (IBS) has been associated with colorectal adenocarcinoma, but its co-occurrence, causal or coincidental, with the more rare neuroendocrine tumor (NET) histology is not well understood.The incidence of carcinoid tumors has been increasing and chronic inflammation can be theoretically associated with carcinogenesis, including the development of carcinoid tumors. We aim to describe the reported literature on patients with IBS who also developed NET and summarize the characteristic findings reported in eachcase. Methods: This is a descriptive retrospective review of all cases of patients with IBD who developed NET reported in literature. We performed a Pubmed search with select keywords for IBS and NET, including ‘Inflammatory bowel disease’, ‘Ulcerative colitis’, ‘Crohn’s disease, and ‘Neuroendocrine Tumors’, or ‘carcinoid’. Extracted information included age, gender, inflammatory bowel disease type, number of years with IBD, treatment received for IBD, tumor site, indication for surgery, the extent of IBD, coexisting tumors, pathological findings, distant metastasis at diagnosis, and survival. Results: Out of 539 articles we identified 87 cases reports between 1970 and 2021. The mean age of patients was 43.61 years. IBS included ulcerative colitis in 46% (40) and Crohn’s disease in 51.7% (45) of patients. The male to female ratio was 1.7:1. The median number of years with IBS before diagnosis of NET was 12.5 years.Of the patients, 36.6% percent (31) were reported to receive treatment for IBS; of these 61.3%(19) were treated with steroids, 42% (13)mesalamine, 29%(9) azathioprine, 12.9% (4) infliximab, 6.4%(2) adalimumab, 3.2%(1) methotrexate, and 3.2% (1) mercaptopurine. Three patients 3.4% (3) initially underwent colectomy with ileostomy. IBS was diffuse in 20.7%(18) of the cases. The ileum was involved in a total of 35.6% (31) and the rectum in 4.6%(4). A mass was found upon regular screening imaging or regular surveillance in 8%(7) of the cases. The NET site was in the rectum in 20.7%(18), in the ileum 19.5%(17), and in the appendix in 19.5%(17). The indication for surgical intervention was due to refractory symptoms in 19.5% (7) of the cases and obstruction in 12.6%(11). About 35.6%(31) of NET cases were reported as well-differentiated, 5.7% (5) as poorly differentiated. Grade was high in 3.4% (3) and low in 5.7%(5) of the cases. Metastasis was reported to lymph nodes in 11.5% (10) and the liver in 5.7%(5). 13.8%(12) had a coexisting adenocarcinoma and 11.5%(10) died from NET. Conclusions: Most NETs in patients with IBS are in younger patients with non-diffuse disease, take a considerable time to develop, are low grade and localize in ileum, appendix and rectum. It is important to consider NET in patients with IBD who develop refractory or obstructive symptoms, especially when considering imaging / endoscopies to assess IBS status and response.