ERBB2 and neoplasm: Combinations of these markers can be used to further subtype the tumor and guide treatment planning, including luminal A (ER+ and/or PR+; HER2−), luminal B (ER+ and/or PR+; HER2+), basal-like (ER−, PR−, and HER2−), and HER2-enriched (ER−, PR−, and HER2+) markers [4].