We noticed two recent studies42,43 demonstrated that TP53, ESR1, PTEN, KMT2C, AKT1, and NF1 were more frequently mutated in the metastatic HR+/HER2− breast cancers compared with the early ones, in accordance with the previous study15, indicating their driving impact in breast cancer metastasis and relapse. This evidence concerns the gene KMT2C and breast cancer.