ERBB2 and breast neoplasm: With the advent of genomic microarray and sequencing technologies, breast tumors have been re-categorized based on the expression of 50 genes, the PAM50 (Prediction Analysis of Microarray 50) gene classification, to five major intrinsic subtypes (Luminal A (LumA/LA), Luminal B (LumB/LB), HER2-enriched, Basal and Normal-like group) [4].