ESR1 and breast neoplasm: Inconsistent results and very high alterations in both estrogen receptor and HER2 status were observed throughout the process of tumor progression.18 Furthermore, different clone mutations in the axillary node with additional copy number changes were demonstrated in a genomic study using single-cell sequencing 19, and few new mutations were not observed in the primary tumor with key driver mutation in synchronous lymph node metastasis.20 These findings indicate difficulty in treating metastatic axillary nodes compared with breast tumors.