Two of the three breast cancer brain metastases samples have primary triple-negative breast cancers, while the other one shows ER (estrogen receptor)/PR (progesterone receptor)/HER2 (human epidermal growth factor receptor 2) positive subtypes according the immunohistochemistry (for ER and PR) and in situ hybridization (for HER2). Here, ERBB2 is linked to triple-negative breast carcinoma.