The majority (70%) of BCs are estrogen receptor‐positive (ER+), meaning the cancer is fueled by the estrogen hormone.[1] ERα is a central transcription factor that is often overexpressed in BC, but also in ovarian, endometrial, and prostate cancers,[2] and plays a crucial role in breast tumorigenesis and proliferation of BC cells. This evidence concerns the gene ESR1 and breast cancer.