ERBB2 and breast cancer: Thus far, PAM50 intrinsic breast cancer subtypes, luminal A (LumA), luminal B (LumB), basal-like (Basal), HER2 over-expressed (HER2), and normal-like (4), which are categorized based on the mRNA expression profile of 50 genes, have received the most attention from BRCA experts, but this classification system was derived based on single-omics only.