The mitotic index (MI) and Ki-67 labeling index have been used as cell proliferative markers in the various tumors. Topoisomerase lIα (Topo lIα) is also expressed in proliferating cells. The aim of this study was to evaluate the correlations between the MI, Ki-67. and Topo lIα expression as proliferative markers of breast cancer.

The cell proliferative activity of 181 breast cancers was measured using MI. Ki-67 labeling index and Topo lIαexpression. The correlation between the measured markers was also analyzed.

The MI, Ki-67, and Topo lIα were significantly correlated with each other(p < 0.000). The MI and Ki-67 labeling index were associated with high histological Grade, and absence of hormone receptor (p < 0.000). Topo lIα expression was correlated with hiGh histolOGical grade (p < 0.000). absence of hormone receptor and HER-2/neu overexpression (p < 0.043).

The MI, Ki-67. and Topo lIα were not associated with any other clinical variables, such as age, tumor size, and lymph node status.

The three proliferative indices were significantly associated with aggressive features of breast cancer, and significantly correlated with each other.