Gene mutations in TP53, KMT2C, RUNX1, AKT1, ESR1, XIRP2, PEAK1, PALB2, MYLK, EVC2 and SLC2A4RG have been reported to be associated with breast cancer metastasis, and their mutation frequency was significantly higher in metastases than in primary tumors. The gene discussed is ESR1; the disease is breast cancer.