title: Ki-ras point mutation in different types of colorectal carcinomas in early stages.
abstract: OBJECTIVE
  The aim of this study was to elucidate pathways of carcinogenesis in the colon and rectum by investigating Ki-ras point mutation in different types of colorectal carcinomas in the early stage.
  
  
  METHODS
  We analyzed rates of Ki-ras codon 12 mutations in 34 small, polypoid-type carcinomas (Tis or T1), 21 superficial-type carcinomas (Tis or T1), and 42 advanced carcinomas (T2, T3, and T4).
  
  
  RESULTS
  Frequency of Ki-ras mutations in superficial-type carcinomas was 14.3 percent (3/21), which was significantly lower than 50 percent (17/34) in small polypoid carcinomas and 40.5 percent (17/42) in advanced carcinomas. These data suggest that another pathway of colorectal carcinogenesis that does not involve Ki-ras point mutation might exist. Among the 17 small polypoid carcinomas with Ki-ras point mutation in which both adenomatous and carcinomatous tissue were examined, 12 showed a mutation of the same type in both carcinomatous and adenomatous tissues. In two cases, mutation was present only in carcinomatous tissue and not in adenomatous tissue; in the other three cases, Ki-ras point mutation was present only in adenomatous tissue but not in carcinomatous tissue.
  
  
  CONCLUSIONS
  These data suggest that carcinoma in a small polypoid lesion does not always develop from pre-existing adenoma with Ki-ras point mutation; in a small number of the polypoid-type early carcinomas, polyclonal composition concerning the Ki-ras gene may exist.
authors.affiliation: Department of Surgery, Jichi Medical School, Tochigi, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Kojima
authors.forename: F
authors.initials: F
authors.lastname: Konishi
authors.forename: T
authors.initials: T
authors.lastname: Tsukamoto
authors.forename: K
authors.initials: K
authors.lastname: Yamashita
authors.forename: K
authors.initials: K
authors.lastname: Kanazawa
mesh_terms: D000230:Adenocarcinoma / Q000235:genetics* / Q000473:pathology; D018256:Adenomatous Polyps / Q000235:genetics / Q000473:pathology; D000368:Aged; D003062:Codon / Q000235:genetics; D003106:Colon / Q000473:pathology; D015179:Colorectal Neoplasms / Q000235:genetics* / Q000473:pathology; D004273:DNA, Neoplasm / Q000235:genetics; D005260:Female; D011905:Genes, ras / Q000235:genetics*; D006801:Humans; D015151:Immunoblotting; D008297:Male; D008875:Middle Aged; D017354:Point Mutation; D016133:Polymerase Chain Reaction; D012007:Rectum / Q000473:pathology
chemical_list: D003062:Codon; D004273:DNA, Neoplasm