The HER2 receptor tyrosine kinase is a clinically-validated molecular target responsible for the initiation, progression and metastasis of a variety of cancers.5 It is an epidermal growth factor receptor, which is highly over-expressed on the cell surface of around 20–30% of breast5 and 20% of gastric cancers6 and has been associated with poorer prognosis. This evidence concerns the gene ERBB2 and cancer.