,2 Important prognostic and predictive factors in patients with early BC (EBC) are: expression of estrogen/progesterone receptors, human epidermal growth factor receptor 2 (HER2) and proliferation markers (e.g. Ki67); number of involved regional lymph nodes; tumour histology, size and grade; and the presence of peritumoral vascular invasion.3 This evidence concerns the gene ERBB2 and breast cancer.