The expression of β-catenin in different subtypes of breast cancer and its clinical significance

The Wnt/beta-catenin signaling pathway is implicated in mammary oncogenesis. Reports of beta-catenin expression and its association with outcome in breast cancer are controversial. This study was performed to address the distribution of beta-catenin expression in invasive breast cancer and the correlation between beta-catenin expression and survival of breast cancer patients, and to determine whether beta-catenin was specifically activated in any molecular subtypes. Immunohistochemistry was performed on a tissue microarray containing 169 invasive breast cancers to detect expression of beta-catenin. One hundred thirty one of the 169 patients were followed up. Correlation between beta-catenin expression and different molecular subtypes was determined using chi-square analysis. Overall survival (OS) was analyzed by Kaplan-Meier method with log-rank test. The invasive breast cancer displayed the different patterns of beta-catenin expression from normal tissues with significantly increased cytoplasmic and nuclear staining of beta-catenin. Aberrant beta-catenin expression was observed in 109 in the 169 cases (64.50 %), and there was no difference in beta-catenin expression in the four molecular subtypes. Furthermore, aberrant beta-catenin expression was significantly associated with adverse outcome not only in the entire cohort but also in each of the different molecular subtypes. beta-catenin activation is preferentially found and is associated with a poor clinical outcome in invasive breast cancer independent of molecular subtype.