As expected, our findings confirm overall higher mutational burden in the metastatic setting, with several key driver genes being significantly more mutated as compared to early stage breast cancer (ESR1, KMT2C, MAP3K1, PTEN, CASP8, EGFR, AKT1, ATM, and RB1) (S3 Fig). This evidence concerns the gene ESR1 and breast carcinoma.