ESR1 and breast carcinoma: The constructed risk signature demonstrated high prognostic accuracy and effectively predicted BRCA molecular subtypes. It showed significant correlations with PR, ER, and HER-2 expression levels, which are critical factors influencing the survival of breast cancer patients. Differential PD-L1 expression, negatively correlated with the risk score, was verified, indicating the potential of this risk signature to guide chemotherapy drug treatment.