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‐cadherin–catenin 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 β‐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 β‐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 β‐catenin maintained their membranous localization, suggesting a functional E‐cadherin–membrane complex.