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Infrequent K-ras codon 12 mutation in serratedadenomas of human colorectum |
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| Authors: | Y Ajioka H Watanabe J Jass Y Yokota M Kobayashi K Nishikura |
| Abstract: | Background—Serrated adenoma is a new morphologicalsubtype of colorectal adenoma. The lesion provides a distinctmorphological route to carcinoma, but the underlying genetic changeshave not yet been investigated. Aims—To determine the frequency ofK-ras mutation in serrated adenoma. Methods—The frequency of K-ras codon12 point mutation in 20 serrated adenomas, five atypical hyperplasticpolyps, and 58sporadic polypoid adenomas was investigated by nestedpolymerase chain reaction-restriction fragment length polymorphism(PCR-RFLP) methods. Results—Although most of the serrated adenomaswere large (average size 11.4 mm) and polypoid, K-rascodon 12 point mutation was detected in only one of the 20 (5%), whichis a significantly lower frequency than that in sporadic polypoidadenomas (18/60; 30%) (p = 0.017). No mutation was detected in theatypical hyperplastic polyps. Three of 20 (15%) serrated adenomascontained a focus of carcinoma in situ, indicating their malignantpotential 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 isuncommon in serrated adenomas, indicating a different spectrum ofgenetic alterations in these lesions from those in typical polypoidsporadic adenomas. This subtype of colorectal adenoma represents a newgenetic pathway in the histogenesis of colorectal carcinoma. Keywords:serrated adenoma; colorectal adenoma; K-ras mutation; PCR-RFLP |
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