KRT19 and cancer: Cyfra21-1, a soluble fragment of cytokeratin19 (CK19) released by cancer cells into circulation (9), plays an important role in diagnosing, predicting and monitoring response to treatment in many kinds of malignancies including non-small cell lung cancer (NSCLC), nasopharyngeal carcinoma, oral/oropharyngeal squamous cell carcinoma, and diagnosis of human papillomavirus infection (10).