ERBB2 and neoplasm: Zhang and collaborators have already also suggested a four-protein signature (brain metastases selected markers (BMSM)) to identify CTCs with potential to metastasize to the brain, demonstrating that HER2+/EGFR+/HPSE+/Notch1+ circulating tumor cells (CTCs) displayed a significant propensity to metastasize to the brain in contrast to the parental CTC cells [59].