Several GISTIC regions (for example, +1p31.3, - 5q14.3, +11q13.3, - 16q23.3) separated ER+ from ER- tumors in HER2+ BC, but their effect was evident also in HER2- tumors (P = 0.06, 5 × 10-23, 0.0002, 0.0003 respectively in HER2- tumors, Bonferroni adjusted t-test). This evidence concerns the gene ESR1 and breast cancer.