Although available targeted therapies for HER2-positive breast cancers have been disappointing in HER2-low breast cancers, Trastuzumab deruxtecan (T-DXd) has demonstrated extremely promising results and can now be utilized maximally not only to treat HER2-positive breast cancers but also this newly discovered HER2-low breast cancer, which could only receive endocrine therapy or chemotherapy prior to Enhertu's approval by the FDA. This evidence concerns the gene ERBB2 and breast cancer.