Cytokeratin 19 fragment is the preferred tumor marker for non-small cell lung cancer, and the elevation of this indicator suggests the presence of a variety of benign and malignant tumors, such as lung, gastrointestinal, urinary and so on. 1. Cytokeratin 19 fragment, also known as CYFRA21-1, has a normal range of 0~3.3ng/ml. Cytokeratin 19 fragment is found in many organs rich in epithelial tissues, such as breast, lung, intestines, bladder, uterus, and so on, and is elevated in benign or malignant lesions in these organs. 2. Cytokeratin 19 fragment is the tumor marker of choice for non-small cell lung cancer, and is mainly used in the differential diagnosis of non-small cell lung cancer and small cell lung cancer. When the cytokeratin 19 fragment is >30ng/ml, there is a high probability of bronchial lung cancer. Cytokeratin 19 fragment can also be used to monitor the efficacy of lung cancer. 3. Elevated cytokeratin 19 fragment can also indicate the presence of other solid tumors such as colorectal cancer, bladder cancer, prostate cancer, breast cancer and other benign diseases such as pneumonia, tuberculosis, chronic bronchitis, urinary system and gynecology. It is recommended that those with abnormal cytokeratin 19 fragment values should seek prompt medical attention for further examination and treatment as prescribed by the doctor.