Although these antibodies have become standard of care and improved overall survival of patients with Her2+ breast cancer, heterogeneity exists within Her2-positive tumours, and the overall response rate to anti-Her2 mAb-based therapies remains modest, approximately 26% when used as a single therapy and 40–60% when used in combination with chemotherapy2,40,41. This evidence concerns the gene ERBB2 and breast carcinoma.