Prevalence and Molecular Biological Feature of Human Aberrant Crypt Foci

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Purpose : To study the nature of human aberrant crypt foci (ACF). Methods: Lower part of rectums in 166 patients who gave informed consent were observed by magnifying chromo-colonoscopy for identifying and counting ACF. 125 biopsy specimens proved to be histologically ACF and were analyzed the sequence of K-ras, exon 1 by using nested PCR and direct sequencing. The sequences of K-ras in 52 hyperplastic polyps were analyzed as a comparison. Results : Median number of ACF counted in patients who had undergone colorectal cancer (CRC) surgery or who had CRC at the time of colonoscopy was the same as that in patients without CRC. Median number of ACF had no significant difference regarding gender, but that of ACF in patients with the age of 70-year or older was greater than that in younger patients (4 versus 2, p<0.0001,). Histologic diagnoses of 125 biopsy specimens were dysplastic ACF in 11, hyperplastic ACF in 26 and non-hyperplastic ACF in 88. Dysplastic ACF can be clearly discriminated from the other histologic types of ACFs, but there were a small number of intermediate type ACFs between hyperplastic ACF and non-hyperplastic ACF.K-ras mutation rates are shown in the table. K-ras mutation rate in hyperplastic ACF is similar to that in hyperplastic polyp. Non-hyperplastic ACF as well as dysplastic ACF showed higher mutation rate than hyperplastic ACF, but K-ras mutantation type was different between non-hyperplastic ACF and dysplastic ACF. Conclusions: Hyperplastic ACF can be regarded as a precursor of hyperplastic polyp. Analysis of K-ras mutant type may suggest that non-hyperplastic ACF and hyperplastic ACF are different from dysplastic ACF.