Objective: Cascades that include β-catenin that has a function in adhesion and interaction with tumor suppressor genes such as APC have important roles in many neoplasms. The aim of the current study was to confirm the effect of the β-catenin pathway in breast tumor carcinogenesis and invasion.

Material and Method: Polyclonal rabbit β-catenin antibody was applied to 52 cases of infiltrative ductal carcinoma and 28 cases of ductal carcinoma in situ using the Avidin Biotin complex immune peroxidase method. The intensity and cellular localization of immunostaining were evaluated and compared.

Results: β-catenin immunoreactivity similar to that of normal epithelium was observed in 7 (8.75%) cases and weak or absent β-catenin expression was noted in 45 (56.25%) infiltrative ductal carcinoma cases. β-catenin expression was strong in 5 (6.25%) cases of ductal carcinoma in situ but weak or absent immunostaining was observed in 23 (28.75%) cases. Membranous β-catenin immunoreactivity was observed in 18 (22.5%) cases of infiltrative and 14 (%17.5) cases of ductal carcinoma in situ. Cytoplasmic immunostaining or complete absence of staining was noted in 34 (42.5%) cases of infiltrative and 14 (17.5%) cases of ductal carcinoma in situ.

Conclusion: Similar quantitative and qualitative changes in β-catenin expression were detected in a considerable proportion of in situ and infiltrative ductal carcinomas in the current study. These findings suggest that β-catenin plays a role in the carcinogenesis of infiltrative ductal carcinoma but similar expression patterns of β-catenin in infiltrative and in situ ductal carcinomas indicates that changes in β-catenin expression occur early in carcinogenesis.