Ki-ras point mutation in different types of colorectal carcinomas in early stages

Dis Colon Rectum. 1997 Feb;40(2):161-7. doi: 10.1007/BF02054981.


Purpose: 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.

MeSH terms

  • Adenocarcinoma / genetics*
  • Adenocarcinoma / pathology
  • Adenomatous Polyps / genetics
  • Adenomatous Polyps / pathology
  • Aged
  • Codon / genetics
  • Colon / pathology
  • Colorectal Neoplasms / genetics*
  • Colorectal Neoplasms / pathology
  • DNA, Neoplasm / genetics
  • Female
  • Genes, ras / genetics*
  • Humans
  • Immunoblotting
  • Male
  • Middle Aged
  • Point Mutation*
  • Polymerase Chain Reaction
  • Rectum / pathology


  • Codon
  • DNA, Neoplasm