In addition, the prognostic impact of topoisomerase IIα expression was clearly dependent on the steroid hormone receptor status of the tumors: no significant difference was observed in patients with tumors negative for estrogen or progesterone receptor (log rank 0.94; P = 0.33; Fig. 3, right panel) whereas detection of topoisomerase IIα in more than 25% of tumor cells identified a subgroup with poor prognosis in receptor-positive breast cancer (log rank 12.0; P = 0.0005; Fig. 3, left panel). Here, PGR is linked to breast cancer.