ERBB2 and cancer: Discordance as high as 18% was found between clinical classification of hormonal receptor-positive and molecular subtyping of luminal cancers, with HR+ cancers often assigned to HER2-enriched and TNBC molecular subtypes, while clinically diagnosed HER2+ and TNBC included a fraction of Luminal cancers by PAM50 assessment [3, 10–17].