CTCs arise during early stages of breast cancer as shown on triple negative breast cancer patients (TBNC), where this cell population at diagnosis is quite heterogeneous in terms of expression of hormone receptors (HR), HER2, or EGFR (varying from 24.4% of expression of HR, 20% for HER2 and 40% for EGFR) while only the HER2 positive CTCs prevail after adjuvant treatment57. Here, ERBB2 is linked to breast cancer.