ERBB2 and breast cancer: In breast cancer, human epidermal growth factor receptor-2 (HER2) inhibitors are widely used to treat patients with HER2-overexpressing or HER2-amplified tumours, but they are less effective in patients with coexisting mutations in fibroblast growth factor receptor-1 (FGFR1) or receptor-2 (FGFR2) genes (Hanker et al., 2017).