Non-small cell lung cancer-associated antigen refers to CYFRA21-1, and elevation may be due to malignant tumors such as non-small cell lung cancer of the lungs, or benign conditions such as pneumonia, requiring further differential diagnosis. Non-small cell lung cancer-associated antigen, also known as cytokeratin 19 fragment, CYFRA21-1, has a normal value of less than 3.3 ng/L. It is mainly found in organs rich in epithelial tissues such as the lungs, bladder, intestines, and mammary glands, and when malignant or benign diseases are present in these organs, CYFRA21-1 will be elevated to varying degrees. Elevated CYFRA21-1 is mainly seen in lung non-small cell lung cancer, but also in bladder cancer, intestinal cancer, breast cancer, etc. Generally, those with malignant tumors have higher elevated values. Elevated CYFRA21-1 is also seen in benign diseases such as mastitis, pneumonia, tuberculosis, cystitis, etc. Generally, CYFRA21-1 is mildly elevated, not exceeding 10ng/L. It is recommended that people with elevated NSCLC-associated antigens should seek prompt medical attention to avoid delaying the disease.