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Infrequent K-ras codon 12 mutation in serrated adenomas of human colorectum
  1. Y Ajiokaa,
  2. H Watanabea,
  3. J R Jassb,
  4. Y Yokotaa,
  5. M Kobayashic,
  6. K Nishikuraa
  1. aFirst Department of Pathology, School of Medicine, Niigata University, Niigata, Japan, bDepartment of Pathology, Medical School, University of Queensland, Queensland, Australia, cThird Department of Internal Medicine, School of Medicine, Niigata University
  1. Dr Y Ajioka, First Department of Pathology, School of Medicine, Niigata University, 1-Asahimachi-dori, Niigata, Japan.

Abstract

Background—Serrated adenoma is a new morphological subtype of colorectal adenoma. The lesion provides a distinct morphological route to carcinoma, but the underlying genetic changes have not yet been investigated.

Aims—To determine the frequency of K-ras mutation in serrated adenoma.

Methods—The frequency of K-ras codon 12 point mutation in 20 serrated adenomas, five atypical hyperplastic polyps, and 58 sporadic polypoid adenomas was investigated by nested polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) methods.

Results—Although most of the serrated adenomas were large (average size 11.4 mm) and polypoid, K-rascodon 12 point mutation was detected in only one of the 20 (5%), which is a significantly lower frequency than that in sporadic polypoid adenomas (18/60; 30%) (p = 0.017). No mutation was detected in the atypical hyperplastic polyps. Three of 20 (15%) serrated adenomas contained a focus of carcinoma in situ, indicating their malignant potential and the existence of a serrated adenoma-carcinoma sequence, but no mutation was detected in the foci of carcinoma in situ.

Conclusions—K-ras mutation is uncommon in serrated adenomas, indicating a different spectrum of genetic alterations in these lesions from those in typical polypoid sporadic adenomas. This subtype of colorectal adenoma represents a new genetic pathway in the histogenesis of colorectal carcinoma.

  • serrated adenoma
  • colorectal adenoma
  • K-ras mutation
  • PCR-RFLP

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