PLAT and neoplasm: Since the discovery of the high level of CKs in BC, several commercially available tumor marker tests have been developed, such as the TPA, tissue polypeptide-specific antigen (TPS) for CKs 8 and 18, tissue polypeptide cytokeratin antigen (TPACYK), and the cytokeratin fragment of CKs 8 and 19 (CYFRA 21-1) [45].