The proper Ki-67 cut-off value in positive hormone receptors (HR+) breast cancer was often discussed due to its importance in evaluating the aggressiveness of the cancer and to distinguish between luminal A and luminal B (HER2−) subtypes when IHC is used as a surrogate classification since both subtypes are of ER+ and HER2− [5, 144]. The gene discussed is NR4A1; the disease is breast cancer.