The currently used blood-based biomarkers for breast cancer, such as cancer antigen (CA) 15-3, CA 27.29, carcinoembryonic antigen (CEA), and soluble human epidermal growth factor receptor 2 (sHER2), are primarily used for prognosis, staging, and therapy monitoring, but have limited utility in detection17–21. This evidence concerns the gene ERBB2 and breast cancer.