title: Frequent co-occurrence of high-grade dysplasia in large flat colonic polyps (>20 mm) and synchronous polyps.
abstract: BACKGROUND
  Large colonic polyps are associated with advanced dysplasia, but prevalence and characteristics of synchronous polyps in patients with large flat colonic polyps are poorly investigated. This study aims to characterize clinicopathological features of large flat colonic polyps and their impact on occurrence and characteristics of synchronous polyps.
  
  
  METHODS
  A total of 802 patients that underwent endoscopic mucosal resection (EMR) of flat colonic polyps >20 mm from 2003 to 2014 in an academic endoscopy unit were retrospectively analyzed for size, location and histology of large polyps and synchronous polyps.
  
  
  RESULTS
  Average size of large polyps was 34.1 mm (range 20-150 mm, standard deviation 16.1 mm). Histology included 52.5 % adenomas with low-grade dysplasia (LGD), 26.7 % with high-grade dysplasia (HGD), 9.6 % serrated polyps and 11.2 % adenocarcinomas. The majority of large polyps were localized in the proximal colon (61 %). 72.2 % of adenocarcinomas were found in the distal colon, while 80.5 % of all serrated polyps were detected in the proximal colon. Increase in polyp size, advanced age and location in the distal colon were associated with presence of HGD/adenocarcinoma in large polyps, as identified by multivariate analysis. Synchronous polyps were detected in 67.2 % of patients undergoing complete colonoscopy during EMR. Presence of HGD/adenocarcinoma in the large polyp, localization of any synchronous polyp in the rectosigmoid colon and occurrence of multiple synchronous polyps were associated with presence of HGD/adenocarcinoma in synchronous polyps.
  
  
  CONCLUSIONS
  Synchronous polyps are frequently found in patients with large flat colonic polyps. The prevalence of synchronous polyps with high grade dysplasia is highest in patients with large flat polyps containing HGD/adenocarcinoma.
authors.affiliation: Division of Signaling and Functional Genomics, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 580, D-69120, Heidelberg, Germany. t.zhan@dkfz.de.|Department of Internal Medicine II, Universitätsmedizin Mannheim, Medical Faculty Mannheim, Heidelberg University, Theodor-Kutzer Ufer 1-3, D-68167, Mannheim, Germany. t.zhan@dkfz.de.
authors.forename: Tianzuo
authors.initials: T
authors.lastname: Zhan
authors.affiliation: Department of Internal Medicine II, Universitätsmedizin Mannheim, Medical Faculty Mannheim, Heidelberg University, Theodor-Kutzer Ufer 1-3, D-68167, Mannheim, Germany. felixshahn@web.de.
authors.forename: Felix
authors.initials: F
authors.lastname: Hahn
authors.affiliation: Division of Biostatistics, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, D-69120, Heidelberg, Germany. t.hielscher@dkfz.de.
authors.forename: Thomas
authors.initials: T
authors.lastname: Hielscher
authors.affiliation: Division of Signaling and Functional Genomics, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 580, D-69120, Heidelberg, Germany. johannes.betge@umm.de.|Department of Internal Medicine II, Universitätsmedizin Mannheim, Medical Faculty Mannheim, Heidelberg University, Theodor-Kutzer Ufer 1-3, D-68167, Mannheim, Germany. johannes.betge@umm.de.
authors.forename: Johannes
authors.initials: J
authors.lastname: Betge
authors.affiliation: Central Interdisciplinary Endoscopy Unit, Universitätsmedizin Mannheim, Medical Faculty Mannheim, Heidelberg University, Theodor-Kutzer Ufer 1-3, D-68167, Mannheim, Germany. georg.kaehler@umm.de.
authors.forename: Georg
authors.initials: G
authors.lastname: Kähler
authors.affiliation: Department of Internal Medicine II, Universitätsmedizin Mannheim, Medical Faculty Mannheim, Heidelberg University, Theodor-Kutzer Ufer 1-3, D-68167, Mannheim, Germany. matthias.ebert@umm.de.
authors.forename: Matthias P
authors.initials: MP
authors.lastname: Ebert
authors.affiliation: Department of Internal Medicine II, Universitätsmedizin Mannheim, Medical Faculty Mannheim, Heidelberg University, Theodor-Kutzer Ufer 1-3, D-68167, Mannheim, Germany. sebastian.belle@umm.de.|Central Interdisciplinary Endoscopy Unit, Universitätsmedizin Mannheim, Medical Faculty Mannheim, Heidelberg University, Theodor-Kutzer Ufer 1-3, D-68167, Mannheim, Germany. sebastian.belle@umm.de.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Belle
mesh_terms: D000230:Adenocarcinoma / Q000453:epidemiology / Q000473:pathology*; D018256:Adenomatous Polyps / Q000453:epidemiology / Q000473:pathology*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003110:Colonic Neoplasms / Q000453:epidemiology / Q000473:pathology*; D003111:Colonic Polyps / Q000453:epidemiology / Q000473:pathology*; D003113:Colonoscopy; D005260:Female; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D009378:Neoplasms, Multiple Primary / Q000453:epidemiology / Q000473:pathology*; D015995:Prevalence; D012189:Retrospective Studies