ESR1 and breast cancer: Depending on the BC subtype, personalized targeted treatment approaches are employed using endocrine therapy (selective estrogen receptor modulators, selective estrogen receptor degraders), aromatase inhibitors, anti-HER2 therapy (trastuzumab, pertuzumab, lapatinib, pyrotinib), and poly adenosine diphosphate (ADP)-ribose polymerase inhibitors (olaparib, talazoparib) [7, 8].