The cfDNA analyzed with a clinical panel of 74 tumor-associated genes revealed diverse subclonal resistance mutations in specific breast subtype such as HER2 mutations in HER2 + disease, PIK3CA mutations in HR + disease or mutual exclusivity of ESR1 mutations and MAPK pathway alterations in HR + HER2 − BC subtype (Turner et al., 2020; Kingston et al., 2021). Here, ERBB2 is linked to breast cancer.