Cytokeratin 19 fragment 4 is not within the normal range of values, but whether it is serious or not can only be determined after specific tests. 1. Cytokeratin 19 is a cellular fragment that generally originates from epithelial cells of alveolar tissue. Under normal circumstances, the normal value of cytokeratin 19 fragment should be less than 3.3ng/ml. when cytokeratin 19 fragment is high, it indicates that there may be an abnormality in a certain part of the body, which leads to accelerated cell metabolism, and at this time, the probability of cell mutation will be increased, which will further lead to an increased risk of cancerous transformation. 2. Currently, cytokeratin 19 fragments play an important role in cancer detection. If the patient’s cytokeratin 19 fragment is high, it is recommended that the patient should go to the hospital for examination in time, through a series of imaging tests such as chest X-ray, CT, etc. to assist in the diagnosis, and carry out treatment under the guidance of the doctor after the results are clarified.