ERBB2 and breast carcinoma: In this prospective cohort composed of relatively homogeneous participants who were all HR-positive/HER2-negative breast cancer patients receiving first-line chemotherapy of docetaxel plus capecitabine, epithelial-to-mesenchymal transition was positively correlated with drug resistance (18, 19), which may lead to the failure in the prognostic prediction of simple total CTC count and epithelial-based CTC-WBC clusters.