Based on inter‐tumour heterogeneity recognized by molecular characterization, breast cancers are categorized as follows: luminal A (ERhigh, Her2low), luminal B (ERlow, Her2low), Her2‐enriched (Her2+, ER‐), basal‐like or triple‐negative (ER‐, PR‐, Her2‐) and claudin‐low (ER‐, Claudinlow, E‐cadherinlow) types, most of which are associated with a poor short‐term prognosis.2 This evidence concerns the gene ERBB2 and breast cancer.