Further evidence that E-cadherin is not a tumour suppressor gene in invasive ductal carcinoma of the breast: an immunohistochemical study

Aims E-cadherin is a cell adhesion molecule expressed in normal breast tissue; it is used generally as a phenotypical marker in breast cancer, with the absence of its expression observed frequently in lobular tumours. We have reported E-cadherin expression previously in 1516 ductal breast carcinoma using tissue microarray (TMA), where 7% of cases showed a complete absence of membrane staining. In this study, we investigated further the existence of E-cadherin-negative ductal carcinoma and evaluated the status of the E-cadherincatenin complex in this subgroup. Material and methods Full-face sections from excision specimens of 72 ductal breast carcinomas reported previously as E-cadherin-negative were assessed morphologically using haematoxylin and eosin staining, and immunohistochemically using two E-cadherin antibodies (HECD-1 and CDH1/4A2C7) and antibodies recognizing -catenin and p120 proteins. Only membrane expression was considered. Results Forty-seven ductal carcinomas were assessed after the exclusion of inappropriate cases; 34 of these showed positive E-cadherin (HECD-1) membrane expression which was focal and weak and seen mainly in invasion fronts. Ten cases showed E-cadherin (4A2C7) staining. Staining for p120 and -catenin showed membrane staining in all cases for both antibodies, which was variable in both intensity and the proportion of positive cells. Conclusion These results demonstrate that E-cadherin-negative ductal carcinoma is rare, and in these cases p120 and -catenin maintained their membranous localization, suggesting a functional E-cadherinmembrane complex.