ERBB2 and neoplasm: Using a signature of 50 genes (PAM50), invasive breast cancer can be differentiated into four major molecular subgroups: luminal A, luminal B, HER2-enriched, and basal-like [3,4,5,6,7,8]; molecular-like subtyping using widely available and cost-effective immunohistochemistry (and in situ hybridization, if needed) +/− tumor grade is used in daily routine diagnostics to estimate these molecular subtypes.