Abstract:Abstract: Objective To investigate the correlations of enhancer of Drosophila zeste homolog 2 (EZH2) with molecular subtypes and clinicopathological parameters of breast cancer. Methods The breast cancers were classified into several molecular subtypes, according to the new standard of molecular classification of breast cancer. The expression of EZH2 in paraffin sections of breast cancer tissues was tested through immunohistochemistry method. The correlations of EZH2 with clinicopathological parameters and new molecular subtypes of breast cancers were analyzed and compared through Chi-square test. The correlation between EZH2 and disease-free survival of the breast cancer patients was analyzed through Kaplan-Meier method. Results In the 13 cases of Luminal A subtype, 3 cases had high EZH2 expression (23.08%). In the 10 cases of Luminal B subtype, 5 cases had high EZH2 expression (50.00%). In the 7 cases of Her-2 over-expression subtype, there were 3 cases of high EZH2 expression (42.86%). In the 12 cases of triple-negative breast cancer subtype, there were 10 cases of high EZH2 expression (83.33%). Significant differences existed in the expression of EZH2 among the four groups of molecular subtypes of breast cancer (P < 0.05). There was significant difference in the disease-free survival between the breast cancer patients with high EZH2 expression and those with low EZH2 expression (P < 0.05). Conclusions EZH2 might be one of the indexes to predict the prognosis of breast cancer.