Non-small cell lung cancer antigen generally refers to non-small cell lung cancer-related antigen, namely cytokeratin 19 fragment (CYFRA21-1), and 3.46ng/ml is a mild elevation, suggesting that diseases of the lung, gastrointestinal tract, gynecology, and urinary system may be present. Cytokeratin 19 fragment, the tumor marker of choice for non-small cell lung cancer, has a normal value of 0-3.3g/ml. Cytokeratin 19 fragment is mainly found in organs rich in epithelial tissues, such as breast, lung, bladder and intestine. When benign or malignant lesions occur in these organs, there will be different degrees of cytokeratin 19 fragment elevation. Cytokeratin 19 fragment 3.46ng/ml is higher than the normal value range, which is a mild increase, and may be caused by pneumonia, tuberculosis, chronic bronchitis, and gynecological diseases, gastrointestinal tract and benign diseases of the urinary system; or it may be caused by malignant tumors, such as non-small-cell lung cancer, bladder cancer, prostate cancer, and so on. It is recommended to combine with other tumor markers, inflammation indicators, chest CT and other examination results to comprehensively determine and analyze the possible causes of the disease, and follow the doctor’s instructions for further examination and treatment.