Polypoid growth and K-ras codon 12 mutation in colorectal cancer

Cancer. 1995 Feb 15;75(4):953-7. doi: 10.1002/1097-0142(19950215)75:4<953::aid-cncr2820750409>3.0.co;2-r.


Background: To clarify genetic changes in colorectal tumorigenesis, K-ras codon 12 point mutations were examined in 101 ordinary colorectal carcinomas and 6 that complicated ulcerative colitis (UC) with special attention to growth patterns.

Methods: The depths of invasion of ordinary carcinoma were submucosa (SMCa) in 39 cases, muscularis propria (PMCa) in 33, and far-advanced in 29. Growth patterns of SMCa and PMCa were classified into three types: polypoid-growth type without central depression (Type 1), polypoid-growth type with central depression (Type 2), and nonpolypoid-growth type. DNA samples were extracted from formalin fixed paraffin embedded sections, and K-ras codon 12 mutations were examined by two-step polymerase chain reaction-restriction fragment length polymorphism.

Results: K-ras mutation frequency was higher in Type 1 SMCa than in nonpolypoid SMCa, 56% (9/16) versus 6% (1/17), respectively, and in PMCa, 78% (7/9) versus 23% (3/13), respectively. In 6 UC carcinomas, a K-ras mutation was detected in only one polypoid carcinoma and none were detected in five nonpolypoid carcinomas.

Conclusions: These results and the authors' previous study suggest that nonpolypoid carcinomas may be derived from flat adenomas, whose K-ras mutation incidence also was low, and this pathway is different from a genetic model based on the ordinary adenoma-carcinoma sequence through polypoid adenomas.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenoma / genetics*
  • Adenoma / pathology
  • Adenomatous Polyps / genetics*
  • Adenomatous Polyps / pathology
  • Adult
  • Aged
  • Base Sequence
  • Codon
  • Colorectal Neoplasms / genetics*
  • Colorectal Neoplasms / pathology
  • Female
  • Genes, ras / genetics*
  • Humans
  • Male
  • Middle Aged
  • Molecular Sequence Data
  • Neoplasm Invasiveness
  • Point Mutation*


  • Codon