Aberrant expression of β-catenin in invasive ductal breast carcinomas

β-catenin has crucial roles in cell-cell adhesion as well as Wingless (Wnt) signaling pathway, which is closely associated with carcinogenesis. The aim of this study was to evaluate the expression of β-catenin in invasive ductal breast carcinomas and investigate its associations with known clinicopathological parameters, estrogen receptor (ER), progesterone receptor (PR) and tumor proliferative activity then, to explore βcatenin expressional differences in primary tumors and corresponding axillary lymph node metastasis (ALNM).

Immunohistochemistry using streptavidin biotin immunoperoxidase method was applied on 65 formalin-fixed paraffin-embedded primary invasive ductal breast carcinomas. Among them, 39 primary tumors (showing LN metastasis) and their corresponding ALNM were further evaluated for differential expression of Βcatenin. Cases were diagnosed during the time period between 2005 to 2007 and retrieved from the archival material of the Pathology Department, Minia University Hospital.

Of the 65 primary tumors, positive staining for β-catenin was observed in 60 (92.3%) cases with membrane and /or cytoplasmic localization in the examined tumor cells. Reduced membrane expression was significantly associated with advanced stage, lymph node metastasis and negative ER. On the contrary, cytoplasmic localization seemed to be related to an aggressive tumor phenotype where significant associations were identified between high cytoplasmic expression and a large tumor size, a high grade, advanced stage, lymph node positivity, high Ki-67 proliferation index and poor Nottingham Prognostic Index. Membrane βcatenin expression was significantly higher in ALNM compared to their primary where it was significantly reduced with re-expression in ALNM.

β-catenin seemed to have different roles in invasive ductal breast carcinomas, based on its expression levels and subcellular distribution. Altered β-catenin expression in primary tumors with re-expression in nodal metastases is a common event in breast ductal carcinomas and may play a central role in establishing metastasis. These results may offer new insights regarding the role of β-catenin in breast cancer.