Involvement of α- and β-catenins and E-cadherin in the development of mammary phyllodes tumours

Aims: Phyllodes tumours (PT) are rare but clinically important fibroepithelial tumours of the breast. beta-Catenin, a key component in Wnt signalling, has been shown to be important in the development of PT. It also functions as a component of the cadherin complex, which may therefore be implicated in PT pathogenesis. By assessing stromal alpha-catenin, beta-catenin and E-cadherin expression in 158 PT cases using immunohistochemistry and examining associations with clinicopathological features, we aimed to determine the role of these proteins in PT pathogenesis. Methods and results: Cytoplasmic beta-catenin correlated with alpha-catenin expression. A significantly higher expression of both markers was observed in borderline than in benign PT (P = 0.003 and <0.001, respectively), but a lower level was found in malignant PT. Cytoplasmic E-cadherin expression was significantly higher in borderline and malignant than in benign PT (P = 0.001 and 0.012, respectively), but was not correlated with other markers. Both E-cadherin and alpha-catenin showed stronger correlations with histological parameters than beta-catenin. alpha-Catenin showed a significant correlation with recurrence (P = 0.005 and 0.016, respectively). Conclusions: alpha- and beta-catenins may be important in the early stages of PT development, while E-cadherin may be required for malignant development. The correlation of alpha-catenin expression with tumour recurrence may be relevant in predicting PT behaviour.