HER2-targeted cancer therapies such as trastuzumab, pertuzumab, trastuzumab emtansine (T-DM1), lapatinib and newer therapies (such as trastuzumab deruxtecan and tucatinib) have significantly improved outcomes for HER2+ metastatic breast cancer (HER2+ MBC) patients [4,5,6,7,8,9]. Here, ERBB2 is linked to cancer.