The prognostic significance of PR has been widely investigated in both luminal A andluminal B (HER2–) tumors, both of which are ER-positive and HER2-negative.10–12 Incontrast, few studies have focused on the importance of PR in luminal B (HER2+)tumors.13,14 We compared the prognostic significance of PR between luminal B (HER2–) andluminal B (HER2+) breast cancer. This evidence concerns the gene ESR1 and breast cancer.