ERBB2 and breast cancer: Zhang et al. characterized EpCAM negative CTCs isolated from primary BC patients and were able to identify a potential BCBM molecular signature, which comprises of four “brain metastases selected markers” (BMSMs); HER2+/EGFR+/HPSE+/NOTCH1+ BMSM+ EpCAM negative CTC lines were highly invasive and, when xenografted in mice, led to the formation of brain and lung metastases [27].