ERBB2 and breast cancer: Breast cancers (BC) are heterogenous in nature and are typically described as luminal A (estrogen/progesterone receptor (ER/PR)+, HER2−, Ki-67−), luminal B (ER/PR+, HER2−, Ki-67+), luminal HER2 (ER/PR+, HER2+), HER2 enriched (ER/PR−, HER2+), Basal-like (ER/PR−, HER2−, EGFR+), and triple-negative (ER/PR−, HER−, EGFR−) [4].