ERBB2 and breast cancer: The growing interest in the ERBB2-low BC subgroup is associated with the rapid development of antibody-drug conjugates.27 Trastuzumab-deruxtecan has shown impressive results compared with standard chemotherapy with an improvement in PFS (HR, 0.50; 95% CI, 0.40-0.63; P < .001) and OS (HR, 0.64; 95% CI, 0.49-0.84; P = .001).28 These results confirm the opportunity of using ERBB2 as a therapeutic vector in ERBB2-low disease and highlight the relevance of this emerging subtype of BC.28