Notably, CTCs that were negative for EpCAM but positive for HER2, EGFR, HPSE, and Notch1 were found to be highly invasive and capable of generating brain and lung metastases when xenografted in nude mice, highlighting the brain competent metastasis signature and limitations of the CellSearch system in capturing these breast cancer circulating cells [125]. Here, ERBB2 is linked to breast cancer.