ERBB2 and breast cancer: Erythroblastic oncogene B (ERBB2), phosphatidylinositol-4,5-bisphosphate 3-kinase, catalytic subunit alpha (PIK3CA), and germline BRCA1/2 alterations are biomarkers confirmed in breast cancer, prospective for the choice of targeted therapies, which are categorized as the highest level of evidence: tier Ia.