title: Colorectal flat neoplasia.
abstract: OBJECTIVE
  An attempt has been made to evaluate the clinicopathological characteristics of flat colorectal neoplastic lesions, and analyse the factors associated with the malignancy.
  
  
  METHODS
  A total of 115 flat neoplastic lesions, > or = 5 mm in size, diagnosed in 87 patients by colonoscopy, were investigated.
  
  
  RESULTS
  The rectum was the most common location. Almost half (49.6%) of the flat neoplasms were small (5-10 mm), 27.8% were 11-20 mm and the remainder (22.6%) larger than 20 mm. The surface was smooth in 55.7%, granular in 20.0% and nodular in 24.3%. Histologically, the flat lesions were tubular, tubulovillous and villous adenomas in 69.6%, 20.9% and 5.2%, respectively. Five lesions (4.3%) were composed of carcinomas without adenoma. High-grade dysplasia, intramucosal carcinoma and invasive carcinoma were diagnosed in 9.6%, 7.8% and 6.1% of all flat neoplasms, respectively. Univariate analysis demonstrated that the location, size, surface pattern and histologic type of the flat lesions were factors associated with malignancy. However, in multivariate analysis, the size of the flat lesions was the only significant risk factor for malignant transformation.
  
  
  CONCLUSIONS
  Flat neoplastic lesions of the colorectum have a relatively high rate of malignancy, and size is the most important factor associated with malignancy.
authors.affiliation: Department of Internal Medicine, Brain Korea 21 Project for Medical Science, Yonsei University College of Medicine, Seoul 120-752, South Korea. kimwonho@yumc.yonsei.ac.kr
authors.forename: Won Ho
authors.initials: WH
authors.lastname: Kim
authors.forename: Jung Hoon
authors.initials: JH
authors.lastname: Suh
authors.forename: Tae Il
authors.initials: TI
authors.lastname: Kim
authors.forename: Sung Kwan
authors.initials: SK
authors.lastname: Shin
authors.forename: Yong Han
authors.initials: YH
authors.lastname: Paik
authors.forename: Hae Won
authors.initials: HW
authors.lastname: Chung
authors.forename: Do Young
authors.initials: DY
authors.lastname: Kim
authors.forename: Jae Hee
authors.initials: JH
authors.lastname: Jeong
authors.forename: Jin Kyung
authors.initials: JK
authors.lastname: Kang
authors.forename: Hoguen
authors.initials: H
authors.lastname: Kim
authors.forename: Nam Kyu
authors.initials: NK
authors.lastname: Kim
mesh_terms: D000230:Adenocarcinoma / Q000473:pathology* / Q000601:surgery; D000236:Adenoma / Q000473:pathology* / Q000601:surgery; D000328:Adult; D000368:Aged; D003113:Colonoscopy; D015179:Colorectal Neoplasms / Q000473:pathology* / Q000601:surgery; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012007:Rectum / Q000473:pathology; D012307:Risk Factors