ERBB2 and breast cancer: This encompasses the era of precision oncology, which has identified breast cancer as a heterogeneous disease, leading to routine substratification of these cancers into four biological distinct, intrinsic molecular subtypes, all of which have varying clinical behaviour, prognoses, treatment strategies, as well as response rates to such treatments (i.e., luminal A breast cancer (LABC), luminal B breast cancer (LBBC), human epidermal growth factor receptor-2 enriched breast cancer (HER2+) and triple-negative breast cancer (TNBC) [6].