KRT18 and carcinoma: In laboratory diagnostics, some of cytokeratins are established noninvasive markers of carcinoma, such as CYFRA 21-1, measuring the soluble cytokeratin-19 fragment; tissue polypeptide antigen (TPA)—measuring the total of cytokeratin 8, 18 and 19; and tissue polypeptide specific antigen (TPS)—measuring soluble cytokeratin 18 fragments [22].