Cytokeratin 19 fragment is an indicator of tumor marker and an important marker of lung cancer, the normal value in the hospital is usually <3.3 ng/mL, 4.333 ng/mL is slightly higher than 3.393 ng/mL, when there are no other tumor markers elevated, there is usually no special significance, and can be regularly rechecked after exclusion of systemic abnormality; when there are several other tumor indicators elevated, it is necessary to go to the hospital for If there are other tumor markers elevated, it is necessary to go to the hospital for further examination to clarify whether there is cancer or not. Cytokeratin 19 fragment is also elevated in epithelial cell carcinoma, mesothelioma, sarcoma and other cancers such as lung cancer, cervical cancer, bladder cancer, breast cancer, and also in some benign diseases such as inflammation, ulcers, polyps and nodules. It is necessary to combine the patient's medical history, symptoms, physical examination and auxiliary examination to make a comprehensive judgment, and cannot rely on a single test index. Cytokeratin 19 fragment 4.33ng/mL is mildly elevated, and should be consulted in the hospital, combined with other tests, to exclude the possibility of tumor.