title: Clinicopathological differences between colonic and rectal carcinomas: are they based on the same mechanism of carcinogenesis?
abstract: BACKGROUND
  There is a difference in the location of colorectal mucosal lesions and invasive cancers.
  
  
  OBJECTIVE
  To ascertain whether the location of colorectal neoplasms reflects the carcinogenesis pathway.
  
  
  METHODS
  The subject material consisted of 4147 neoplastic lesions that had been resected endoscopically or surgically from 5025 patients. Mucosal lesions and submucosal cancers were classified into depressed and non-depressed types endoscopically or histologically. The relations between macroscopic type, size, histology, and location were investigated.
  
  
  RESULTS
  (a) Non-depressed type. A total of 1774 of 3454 (51%) mucosal lesions were located in the right colon, 1212 (35%) in the left colon, and 468 (14%) in the rectum. The incidence of mucosal lesions larger than 10 mm was 10% (185/1774) in the right colon, 21% (254/1212) in the left colon, and 27% (127/468) in the rectum. The incidence of mucosal lesions with villous components was 2% (32/1774) in the right colon, 5% (63/1212) in the left colon, and 13% (62/468) in the rectum. The ratio of submucosal cancers to mucosal lesions was significantly higher in the rectum (0.064, 30/469) than in the left (0.034, 43/1279) or right (0.010, 18/1857) colon. (b) Depressed type. The incidences of depressed type mucosal lesions and submucosal cancers were 5% (83/1857) and 17% (3/18) in the right colon, 5% (67/1279) and 5% (2/43) in the left colon, and 0.2% (1/469) and 0% (0/30) in the rectum, respectively.
  
  
  CONCLUSIONS
  There may be some mechanisms that promote the progression of mucosal lesions to invasive cancers in the left colon and rectum, whereas a de novo pathway from depressed type lesions may be implicated in some cancers of the right colon.
authors.affiliation: Department of Gastrointestinal Oncology and Gastroenterology, National Cancer Centre Hospital East, Chiba, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Konishi
authors.forename: T
authors.initials: T
authors.lastname: Fujii
authors.forename: N
authors.initials: N
authors.lastname: Boku
authors.forename: S
authors.initials: S
authors.lastname: Kato
authors.forename: I
authors.initials: I
authors.lastname: Koba
authors.forename: A
authors.initials: A
authors.lastname: Ohtsu
authors.forename: H
authors.initials: H
authors.lastname: Tajiri
authors.forename: A
authors.initials: A
authors.lastname: Ochiai
authors.forename: S
authors.initials: S
authors.lastname: Yoshida
mesh_terms: D000236:Adenoma / Q000473:pathology; D002471:Cell Transformation, Neoplastic; D003110:Colonic Neoplasms / Q000473:pathology* / Q000601:surgery; D003113:Colonoscopy; D018450:Disease Progression; D006801:Humans; D009361:Neoplasm Invasiveness; D012004:Rectal Neoplasms / Q000473:pathology* / Q000601:surgery