Consistent with previous studies, luminal breast cancers exhibit a greater frequency of HER2-low tumors in contrast to TNBC.13,28–30 The analysis of ctDNA from 1071 MBC patients revealed that among the 488 HER2-low MBC patients, TP53, PIK3CA, and ESR1 exhibited the highest frequency of mutations. Here, TP53 is linked to breast cancer.