Circulating tumor cells (CTCs) and circulating tumor DNA (ctDNA) in patients with metastatic breast cancer can be detected by the CellSearch System (Veridex LLC, Raritan, NJ, USA) [18], which recognizes epithelial-cell adhesion molecules (cytokeratins 8, 18, and 19), and PCR [19], respectively. This evidence concerns the gene EPCAM and neoplasm.