The advent of a range of HER2 targeted therapies, including the monoclonal antibody trastuzumab, significantly improved outcomes for patients with this subtype of breast cancer but only about one third of women demonstrate tumour regression with trastuzumab monotherapy and many patients treated with trastuzumab plus chemotherapy still develop progressive disease within one year [1,2,3]. Here, ERBB2 is linked to breast carcinoma.