ESR1 and breast cancer: In addition, validation in different databases showed that the mRNA levels of AKT1, ESR1, HSP90AA1, CASP3, SRC and MDM2 are increased in BC tissues, which may contribute to the occurrence of BC; AKT1, ESR1, CASP3 and SRC may be used as molecular markers in patients with different stages of BC, and ESR1, IGF1 and HSP90AA1 may be used as prospective biomarkers for the diagnosis and prognosis of BC.