In addition, AIB1 amplification correlates in primary breast cancers with ERα positivity and tumor size [59, 60] and, very recently, it has been proposed that, in ERα-positive/HER2-negative invasive breast carcinoma, AIB1 could serve as a new putative prognostic biomarker, with its expression (high AIB1 vs low AIB1) being associated to breast cancer mortality [61]. This evidence concerns the gene ESR1 and breast cancer.