ERBB2 and breast cancer: Breast cancer, recognised as a diverse disease, is classified into five unique molecular subtypes using the PAM50 gene expression profile, including luminal A (LABC), luminal B (LBBC), HER2-enriched (HER2+), basal-like and normal-like (Sinn and Kreipe, 2013; Ward et al., 2015; Tang et al., 2016; Marinello et al., 2019).