Endoscopic indicators in patients with familial adenomatous polyposis undergoing duodenal resections – a nationwide Danish cohort study with long-term follow-up

Background: Familial adenomatous polyposis (FAP) predisposes individuals to duodenal adenomas. This study describes the histopathological features of endoscopic and surgical specimens from the duodenum, as well as genotype-phenotype associations. Methods: All known FAP patients were included from the Danish Polyposis Register. FAP patients were defined as having more than 100 cumulative colorectal adenomas and/or having a known germline pathogenic variant in the APC gene. Endoscopic procedures, histopathology, and genetics were evaluated. Results: Of 500 FAP patients, 70.6