It has the advantage of relieving symptoms in 60–90% of patients [11,12,13], achieving local control in 60–100% [12,14], and enabling diagnostic testing for biomolecular markers, which may differ from the primary tumor; for example, expression of therapeutically targetable receptors for estrogen, progesterone and/or epidermal growth factor (ER/PR/HER2) is discordant in 20–50% of breast cancer cases [15,16]. The gene discussed is ERBB2; the disease is breast cancer.