ERBB2 and breast neoplasm: Since its first implementation in 1941 [1], a great variety of IHC biomarkers have been validated and employed in clinical and research laboratories for characterization of specific cellular events [2], e.g., the nuclear protein Ki-67 associated with cell proliferation [3], the cellular tumor antigen P53 associated with tumor formation [4], and the human epidermal growth factor receptor 2 (HER2) associated with aggressive breast tumor development [5].