Prognostic Significance of Combining Cytokeratin-19, E-Cadherin and Ki-67 Analysis in Triple-Negative Breast Cancer with Basal-Like and Non-Basal-Like Phenotype

Triple-negative breast cancer (TNBC) is known to have the worst outcome compared to the other forms of breast cancer. Moreover, molecular markers identified basal-like breast cancer (BLBC) phenotypes to be also related to a worse prognosis. In this study, we evaluated by immunohistochemistry (IHC) the prognostic significance of combining Cytokeratin-19 (CK19), E-cadherin, and Ki-67 tissue expression in triple-negative breast cancer (TNBC) cases presenting a basal-like (BLBC) or a non-basal-like (n-BLBC) phenotype to improve the selection and the monitoring of BC patients with a more aggressive outcome. Herein, when compared to n-BLBC, patients with BLBC showed a positive correlation with lymph node metastasis occurrence and lower survival rates. Immunohistochemistry analysis revealed significantly lower E-cadherin prevalence and higher prevalence of both CK19 and Ki-67 in BLBC when compared to n-BLBC. Spearman correlation showed that E-cadherin is negatively and significantly correlated to CK19 and Ki-67 expressions. Moreover, in BLBC, expressing both CK19 and Ki-67 combined with E-cadherin loss was associated with the worst relapse-free and overall survival. In conclusion, TNBC/BLBC phenotypes simultaneously losing E-cadherin and overexpressing CK19 and Ki-67 markers are the most aggressive forms. This combined analysis could be a predictive marker of poor prognosis.