ESR1 and neoplasm: Breast cancer is a molecularly heterogeneous disease, with treatment strategies guided by specific molecular targets such as receptor tyrosine kinases (e.g., EGFR and HER2), hormonal receptors (ER and PR), and key regulatory proteins involved in tumor progression, including PIK3CA, CDKs, and tubulin [5, 26, 27, 55, 60].