Current treatment for hormone-dependent postmenopausal BCa patients consists of two strategies to reduce the effects of estrogens on tumor growth: blocking estrogen binding to estrogen receptor (ER) with antiestrogens (e.g. tamoxifen) or inhibiting estrogen synthesis with aromatase inhibitors (AIs, e.g. exemestane, anastrozole and letrozole) [1]. Here, ESR1 is linked to neoplasm.