ERBB2 and breast cancer: Using profiles of gene expression, breast cancers are divided into five major subtypes: triple-negative (ER-/PR-/HER2-), luminal A (ER/PR+,HER2-), luminal B (ER/PR/HER2+), HER2+/ER-, and normal breast-like (ER/PR/HER2-, CK5/6,HER1+) [14-16].