Clinicopathological and molecular analyses of linearly expanded epithelial cells with ß-catenin alterations, "ß-catenin signature", in the normal fallopian tube.

ABSTRACT

AIMS: Recent advances in next-generation sequencing have made it clear that clonal expansion of cells harbouring driver gene mutations occurs in physiologically normal epithelium. Molecular analysis of tubal epithelium has been almost exclusively confined to the TP53 pathway, which is involved in serous carcinogenesis. Other oncogenic events have not been explored in detail. Here, we report the linear expansion of fallopian tubal epithelial cells exhibiting an altered ß-catenin profile (ß-catenin signature). Through molecular analyses, we determined the incidence and clinicopathological significance of ß-catenin signatures. METHODS AND RESULTS: We evaluated 64 specimens of surgically removed bilateral fallopian tubes. Thirty-three ß-catenin signatures were identified in 13 cases (20.3%); these patients were significantly younger than those without ß-catenin signatures (median ages of 44 and 57 years, respectively, P = 0.0317). No correlation between ß-catenin signature and any clinical factor was observed. CTNNB1 mutations were detected in three of eight ß-catenin signatures when tissues were microdissected and subjected to Sanger sequencing in two representative cases. CONCLUSIONS: This is the first report of the CTNNB1 mutation in clusters of morphologically bland tubal epithelial cells. The results of this study indicate that ß-catenin signatures are common, and they may be a part of diverse molecular alterations occurring in normal tubal epithelium.