It is well documented that patients with HER2 overexpressing tumours seem to have a higher incidence of intracranial metastases (up to 30%) (Clayton et al, 2004), and the brain is often described as a ‘sanctuary site’ because of difficulties with cytotoxic agents or monoclonal antibodies such as trastuzumab crossing the ‘blood–brain barrier’. The gene discussed is ERBB2; the disease is neoplasm.