Epithelial Paradox: Clinical Significance of Coexpression of E-cadherin and Vimentin With Regard to Invasion and Metastasis of Breast Cancer

E-cadherin and vimentin are regarded as major conventional canonical markers of epithelial–mesenchymal transition. Both E-cadherin– and vimentin-positive tumors had the worst prognosis among all cases. Further, E-cadherin and vimentin protein is colocalized within the same tumor cells, suggesting the existence of an aggressive subpopulation in the primary tumor nest of breast cancer. Background: E-cadherin and vimentin are regarded as major conventional canonical markers of the epithelial–mesenchymal transition. It is commonly assumed that E-cadherin is uniformly lost during the process of epithelial–mesenchymal transition. Breast tumor cells typically invade as a cohesive multicellular unit in a process called collective invasion. The aim of this study was to reveal the clinical importance of the expression pattern of E-cadherin and vimentin in breast cancer. Methods: E-cadherin and vimentin protein expression was evaluated by immunohistochemistry in 176 invasive breast cancer samples. Among these, E-cadherin and vimentin expression were evaluated in the set of primary site and metastatic lymph nodes in 65 cases. In addition, E-cadherin and vimentin expression were analyzed by confocal laser scanning microscopy to see E-cadherin and vimentin localization in the breast cancer cells. Results: Both at the primary site and metastatic lymph nodes, both E-cadherin– and vimentin-positive tumors had the worst disease-free and overall survival among all cases. In addition, E-cadherin and vimentin protein is colocalized within the same tumor cells in a human breast cancer specimen. Conclusion: Our present data suggest the existence of an aggressive subpopulation in the primary tumor nest of breast cancer.