ERBB2 and breast cancer: The estimated frequency of BMs ranges from 20–30% in patients with HER2-positive breast cancer and TNBC, whereas it is less than 10% in patients with the luminal subtype [108].HER2 promotes the phosphorylation of proteins across multiple signaling pathways, suppresses pro-apoptotic proteins, and enhances the expression of genes related to cell proliferation, processes that contribute to epithelial-mesenchymal transition (EMT) and increase the risk of brain metastasis [194–196].