Cytokeratin 19 fragment is high 3.89 can be seen in non-small cell lung cancer, also can be seen in pneumonia and other benign diseases, need to clarify the etiology. 1. cytokeratin 19 is mainly distributed on monolayer epithelial cells, and under normal conditions, the serum cytokeratin 19 fragment is less than 3.3ng/ml. when epithelial cells become cancerous, it can lead to the appearance of a large amount of cytokeratin 19 fragment in the serum. 2. Common causes of elevated cytokeratin 19 fragment values include: (1) Cytokeratin 19 fragment has high diagnostic value for lung cancer, especially for non-small cell lung cancer, and is the marker of choice for non-small cell lung cancer with a sensitivity of 80%. It is both early diagnosis and related to the growth of mass, and can be used as an important indicator for follow-up, observation of efficacy and judgment of prognosis. (2) In addition, it has a high positive rate for bladder cancer, pancreatic cancer, gallbladder cancer; cervical cancer, colon cancer, stomach cancer can also be increased. (3) Benign diseases: such as pneumonia, tuberculosis, chronic bronchitis, gastrointestinal diseases, gynecological diseases, and urological diseases, etc. CYFRA 21-1 levels are also elevated, but mildly. Cytokeratin 19 fragment value of 3.89ng/ml alone can not accurately determine the cause of the test results, but also need to be combined with the characteristics of the medical history, other test results in order to make an accurate judgment, it is recommended that timely regular hospital consultation, by a professional doctor to determine the cause.