Lower incidence of K-ras codon 12 mutation in flat colorectal adenomas than in polypoid adenomas

Jpn J Cancer Res. 1994 Feb;85(2):147-51. doi: 10.1111/j.1349-7006.1994.tb02075.x.


In order to clarify genetic changes in flat adenomas, K-ras codon 12 point mutations were examined in 56 flat adenomas, 81 polypoid adenomas and 42 cancers of colon and rectum. The mutation frequency in flat adenomas was 23% (13/56), significantly lower than that in polypoid adenomas (67%: 54/81) and cancers (76%: 32/42). Even mildly dysplastic adenomas or small (less than 5 mm) adenomas showed higher mutation incidence in polypoid type (62%, 57%) than in flat type (23%, 19%). Among flat adenomas, flat elevated lesions exhibited relatively higher mutation frequency than completely flat or depressed ones. As for cancers, 14 tumors (33%) contained mutations only in a minor tumor cell population, indicating that these mutations occur at a late stage of tumorigenesis. These results suggest that the adenoma-carcinoma sequence through flat adenomas may be different from that through polypoid adenomas, and genetic changes may be heterogeneous in colorectal carcinogenesis.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenoma / genetics*
  • Adenoma / pathology
  • Adenomatous Polyps / genetics*
  • Adenomatous Polyps / pathology
  • Base Sequence
  • Colorectal Neoplasms / genetics*
  • Colorectal Neoplasms / pathology
  • DNA Mutational Analysis
  • DNA Primers
  • DNA, Neoplasm / genetics
  • Gene Frequency
  • Genes, ras*
  • Humans
  • Molecular Sequence Data
  • Mutation*
  • Polymerase Chain Reaction
  • Sensitivity and Specificity


  • DNA Primers
  • DNA, Neoplasm