EZH2 overexpression was significantly associated with the proliferative index, with 25.7 % (19/74), 68.5 % (50/73), and 87.3 % (69/79) of breast carcinomas having overexpression with a low (Ki67 < 14 %), moderate (Ki67 14 ~ 30 %) or high (Ki67 ≥ 30 %) proliferative index, respectively (Chi-square, p < 0.001). The gene discussed is MKI67; the disease is breast carcinoma.