These associations could increase the magnitude of efficacy in a given HER2+ BC setting and/or extend the landscape of treatment applicability in terms of biological characteristics, such as anti-HER2 vaccine-based immunotherapy plus trastuzumab for HER2 IHC1+/2+ BC or anti-HER2 vaccines for HER2 IHC3+ DCIS; or expand treatment possibilities in terms of clinical setting, such as the use of anti-HER2 vaccines in the metastatic/neoadjuvant setting or immune checkpoint inhibition in the early disease. This evidence concerns the gene ERBB2 and breast cancer.