ERBB2 and breast carcinoma: Using gene expression profiling, breast cancer has been classified into five molecular subtypes: luminal A, luminal B, epidermal growth factor receptor 2‐enriched (HER2+), basal‐like, and normal‐like breast cancers (Cancer Genome Atlas Network, 2012; Perou et al., 2000; Riaz et al., 2013).