||Cytokeratin19 Fragment Antigen 21-1(CYFRA21-1) belongs to a family of 20 related polypeptides that are constituents of the intermediate filaments of epithelial cells. Of these CK19 is the most frequently expressed cytokeratin endometrial cancer. CYFRA21-1 is a common tumor marker of lung cancer,non-small-cell cancer, small cell carcinoma and squamous cell carcinoma. For breast cancer, CYFRA21-1 may be comparable to the sensitivity and specificity of CA153.Measured jointly with any of the tumor markers as CEA, SCCA, NSE, can increase the sensitivity. Other as bladder cancer, nasopharyngeal cancer, ovarian cancer, gastrointestinal cancer, and also have certain positive rate. CYFRA21-1 in hepatitis, pancreatitis, pneumonia, benign prostatic hyperplasia may also be increased.