Patients presented BM during their metastatic disease in 19% of ER+/HER2–, 34% of ER+/HER2+, 49% of ER–/HER2+ and 38% of triple-negative metastatic breast cancers.2 The development of BM in triple-negative BC patients frequently occurs with concurrent extracranial disease progression,18 in contrast with HER2-overexpressed BM, which often occurs with a stable extracranial status.24 BM-free survival (BM-FS) rates at 5 years were 68%, 50% and 30% for ER+/HER2–, ER+/HER2+ and ER– subtypes, respectively. Here, ERBB2 is linked to glycogen storage disease VI.