Abstract
There have been two hypotheses concerning the histogenesis of colorectal carcinoma : adenoma-carcinoma sequence and de novo carcinogenesis. Although the importance of K-ras mutation has been accepted regarding carcinogenesis, few studies have looked at the correlation between K-ras mutation and the feature of atypical glands demonstrated in epithelial tumors that arise in the colorectal epithelium. In partricular, it remains obscure how K-ras mutation influcences phenotypical characteristics of an epithelial tumor, e.g. tubular, villous, and others. The present study describes the incidence and variety of K-ras mutation in each independent histological component comprising epithelial neoplastic lesions of the large intestine of less than 10mm diameter. As the result, it was extensively rare for a small lesion entirely composed of villous component obtained from any groups of lesions to show the highest incidence of K-ras mutation. Then, a tubular component generally indicated lower incidence, but those obtained from the groups having an area of villous components were high. Accordingly, K-ras mutation may advance the phenoconversion from tubular to villous configuration in colorectal lesions of epithelial neoplasia.
