The predilection to metastasise to the CNS differs by BC subtype, with the incidence of BCBM ranging between 8% and 50%, with patients with HER2-positive and TN BC having the highest incidence.5, 6, 7, 8 BCBMs are known to differ at the histological and molecular level from their primary tumour.8 Here, ERBB2 is linked to breast cancer.