ERBB2 and neoplasm: HER2 is a member of the epidermal growth factor receptors (EGFRs) family, which is composed of four members, namely HER1, HER2, HER3 and HER4.5 Tumours with HER2 overexpression respond to targeted therapy with the anti-HER2 antibody trastuzumab and this treatment is associated with improved survival.