CEACAM5 and head and neck squamous cell carcinoma: Cytokeratin 19 serum fragment 21-1 (Cyfra21-1), squamous cell carcinoma-associated antigen (SCCAg), tissue polypeptide-specific antigen (TPS), carcinoembryonic antigen (CEA), Fe protein, and circulating tumor cells (CTCs) are tumor markers for the diagnosis and prognosis of HNSCC [15].