ERBB2 and breast cancer: There is a high incidence of BM among breast cancer patientswith primary tumors overexpressing the HER2 receptor (HER2+ breastcancers) and in triple-negative breast cancers (those lacking expressionof estrogen and progesterone receptors, as well as HER2).1 The presence of BM is frequently diagnosed late,after presentation of neurological symptoms once the disease burdenis significant in the brain.2