This molecular abnormality defines breast tumours with poor prognosis and increased risk of early relapse (Slamon et al, 1987, 1989), but predicts response to the humanised monoclonal anti-HER2 antibody trastuzumab (Herceptin) or to small tyrosine kinase inhibitors such as lapatinib or erlotinib. Here, ERBB2 is linked to breast neoplasm.