title: Clinicopathological, endoscopic, and molecular characteristics of the "skirt" - a new entity of lesions at the margin of laterally spreading tumors.
abstract: OBJECTIVE
  A slightly elevated flat lesion with wide pits has occasionally been observed at the margin of laterally spreading tumors (LSTs) and is known as a "skirt." The aim of this study was to evaluate the clinicopathological, endoscopic, and genetic characteristics of a skirt.
  
  
  METHODS
  Consecutive LSTs were examined to evaluate the pathological, endoscopic, and genetic characteristics. Pathological characteristics, including the dimension of the cryptic opening (DCO), width of the individual gland (WIG), DCO to WIG ratio, and microvessel diameter were elucidated and compared with those of hyperplastic polyps, low grade dysplasia (LGD), and normal mucosa. The endoscopic findings of pit and microvascular patterns were assessed. Gene mutation analyses were performed for the KRAS, BRAF, NRAS, and PIK3CA genes.
  
  
  RESULTS
  A skirt was identified in 35 of 1023 LSTs, and 80 % of lesions with a skirt had a component of either intramucosal or submucosal adenocarcinoma. The DCO, WIG, and DCO to WIG ratio of the skirt were significantly larger than those of other lesions. The microvessel diameters in skirts were significantly smaller than those in LGDs. Regarding the endoscopic findings, 30 skirts showed pits with a coral reef-like appearance, and all skirt regions were found to have a type I capillary pattern. KRAS mutation at codon 146 was found in the nodular part in one of five LSTs with a skirt.
  
  
  CONCLUSIONS
  The skirt is a newly identified lesion distinct from hyperplastic polyps and LGDs, suggesting the presence of a novel pathway for rectal carcinogenesis from LSTs with a skirt.
authors.affiliation: Department of Gastroenterology, Endoscopy Division, National Cancer Center Hospital East, Kashiwa, Chiba, Japan.
authors.forename: Shozo
authors.initials: S
authors.lastname: Osera
authors.affiliation: Pathology Division, Research Center for Innovative Oncology, National Cancer Center Hospital East, Kashiwa, Chiba, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Fujii
authors.affiliation: Department of Gastroenterology, Endoscopy Division, National Cancer Center Hospital East, Kashiwa, Chiba, Japan.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Ikematsu
authors.affiliation: Department of Gastroenterology, Endoscopy Division, National Cancer Center Hospital East, Kashiwa, Chiba, Japan.
authors.forename: Hideaki
authors.initials: H
authors.lastname: Miyamoto
authors.affiliation: Department of Gastroenterology, Endoscopy Division, National Cancer Center Hospital East, Kashiwa, Chiba, Japan.
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Oono
authors.affiliation: Department of Gastroenterology, Endoscopy Division, National Cancer Center Hospital East, Kashiwa, Chiba, Japan.
authors.forename: Tomonori
authors.initials: T
authors.lastname: Yano
authors.affiliation: Pathology Division, Research Center for Innovative Oncology, National Cancer Center Hospital East, Kashiwa, Chiba, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Ochiai
authors.affiliation: Department of Gastroenterology and Gastrointestinal Oncology, National Cancer Center Hospital East, Kashiwa, Chiba, Japan.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Yoshino
authors.affiliation: Juntendo University Graduate School of Medicine, Tokyo, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Ohtsu
authors.affiliation: Department of Gastroenterology, Endoscopy Division, National Cancer Center Hospital East, Kashiwa, Chiba, Japan.
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Kaneko
mesh_terms: D000328:Adult; D000368:Aged; D063646:Carcinogenesis / Q000235:genetics / Q000473:pathology; D003111:Colonic Polyps / Q000473:pathology*; D003113:Colonoscopy / Q000379:methods*; D015179:Colorectal Neoplasms / Q000175:diagnosis* / Q000235:genetics; D005260:Female; D006801:Humans; D007413:Intestinal Mucosa / Q000098:blood supply / Q000000981:diagnostic imaging / Q000473:pathology; D007564:Japan; D008297:Male; D055806:Microvessels / Q000473:pathology; D008875:Middle Aged; D009154:Mutation; D048493:Proto-Oncogene Proteins B-raf / Q000235:genetics; D016283:Proto-Oncogene Proteins p21(ras) / Q000235:genetics; D012039:Regional Blood Flow; D013223:Statistics as Topic
chemical_list: C117307:KRAS protein, human; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf; D016283:Proto-Oncogene Proteins p21(ras)