Primary breast tumour hormone receptor status (Estrogen receptor (ER), Progesterone Receptor (PR) and Human EGFR Receptor 2 (HER2)) can be used as prognostic markers for brain metastasis risk10,11 and BBM occurs more frequenty in patients with ER–, HER2 + or triple negative breast tumours (ER-/PR-/HER2-)12. The gene discussed is ESR1; the disease is breast neoplasm.