Very briefly, breast tumors are traditionally classified into Luminal A-like tumors (LumA-l), Luminal B-like tumors (LumB-l), HER2-like tumors (HER2-l), and Basal-like (Basal-l), defined by immunohistochemistry or mRNA levels of key receptors (ESR1, PGR and ERBB2) and proliferative biomarkers (Sørlie et al, 2001). Here, ERBB2 is linked to breast neoplasm.