ERBB2 and breast carcinoma: Based on the immunostaining data from five markers [estrogen receptor-α (ER-α), progesterone receptor (PR), HER2, cytokeratin (CK) 5/6, and epidermal growth factor receptor (EGFR)], breast carcinoma can be categorized as luminal A (ER-α + and/or PR+ and HER2-); luminal B (ER-α + and/or PR+ and HER2+); HER2-overexpressing (ER-α- and PR- and HER2+); basal-like (ER-α-, PR-, HER2- and EGFR or CK 5/6+); and unclassified (ER-α-, PR-, HER2-, EGFR-, and CK 5/6-) [8, 9].