title: Clinicopathologic characteristics and malignant potential of colorectal flat neoplasia compared with that of polypoid neoplasia.
abstract: OBJECTIVE
  Because of their potential for malignancy, flat colorectal neoplasias are a current topic of debate. This study was designed to investigate the clinicopathologic features of flat neoplasia and to compare them with those of polypoid neoplasia, as well as to identify the determinants of malignant transformation of both flat and polypoid colorectal neoplasia.
  
  
  METHODS
  A prospective, cross-sectional study of 3,360 patients diagnosed with adenomas via total colonoscopy and polypectomy was performed at 11 tertiary medical centers between July 2003 and July 2004. In this study, potential risk factors for malignant transformation were analyzed. If multiple adenomas were identified, then only the adenoma with the most advanced degree of histology was recorded for the patient.
  
  
  RESULTS
  Of a total of 3,360 neoplasias identified, we found that the incidence of flat and polypoid neoplasias were 207 (6.2 percent) and 3,153 (93.8 percent), respectively. Patients with flat neoplasias tended to be older (59.6 vs. 57.1, P < 0.01), with the neoplasia located more frequently in the right colon than polypoid neoplasias (49.3 percent vs. 32 percent, P < 0.01). The incidence of high-grade dysplasia or cancer in flat neoplasias was similar to that of polypoid neoplasias (5.4 percent vs. 4.6 percent, P = 0.36). Multivariate analysis revealed that a size of > or =11 mm (odds ratio, 6.8; 95 percent confidence interval, 4.8-9.7) and location in the left colon (odds ratio, 1.6; 95 percent confidence interval, 1.1-2.4) were significant determinants for the malignancy potential of colonic neoplasias.
  
  
  CONCLUSIONS
  The clinicopathologic indices for the propensity of malignant transformation in colorectal neoplasias were a size > or =11 mm and location in the left colon rather than flat gross morphology.
authors.affiliation: Department of Internal Medicine and Institute of Lifelong Health, Yonsei University, Wonju College of Medicine, 162 Ilsan-dong, Wonju, South Korea.
authors.forename: Dong Hun
authors.initials: DH
authors.lastname: Park
authors.forename: Hyun Soo
authors.initials: HS
authors.lastname: Kim
authors.forename: Won Ho
authors.initials: WH
authors.lastname: Kim
authors.forename: Tae Il
authors.initials: TI
authors.lastname: Kim
authors.forename: Young Ho
authors.initials: YH
authors.lastname: Kim
authors.forename: Dong Il
authors.initials: DI
authors.lastname: Park
authors.forename: Hyo Jong
authors.initials: HJ
authors.lastname: Kim
authors.forename: Suk-Kyun
authors.initials: SK
authors.lastname: Yang
authors.forename: Jeong-Sik
authors.initials: JS
authors.lastname: Byeon
authors.forename: Moon Sung
authors.initials: MS
authors.lastname: Lee
authors.forename: Il Kwun
authors.initials: IK
authors.lastname: Chung
authors.forename: Sung Ae
authors.initials: SA
authors.lastname: Jung
authors.forename: Yoon Tae
authors.initials: YT
authors.lastname: Jeen
authors.forename: Jai Hyun
authors.initials: JH
authors.lastname: Choi
authors.forename: Hwang
authors.initials: H
authors.lastname: Choi
authors.forename: Dong Soo
authors.initials: DS
authors.lastname: Han
mesh_terms: D000236:Adenoma / Q000453:epidemiology / Q000473:pathology*; D000368:Aged; D001706:Biopsy; D002471:Cell Transformation, Neoplastic; D003111:Colonic Polyps / Q000453:epidemiology / Q000473:pathology*; D003113:Colonoscopy; D015179:Colorectal Neoplasms / Q000453:epidemiology / Q000473:pathology*; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D011230:Precancerous Conditions / Q000453:epidemiology / Q000473:pathology*; D011446:Prospective Studies