NSE, neuron-specific enolase, is the preferred marker for detecting small cell lung cancer, and if it is elevated more than 3-fold, further testing is needed to rule out tumor possibilities. NSE is a non-specific tumor marker and is found to be elevated in 60%-81% of small cell lung cancer cases. NSE is normal up to 20ng/ml and may have no real clinical significance if mildly elevated, such as in certain benign lung lesions and brain lesions, where NSE can also be slightly elevated. However, if laboratory tests reveal a 3-fold or more elevated NSE, especially a more than 10-fold elevation, one needs to be alert to tumor conditions. However, it is worth noting that no matter how high the NSE is, it cannot directly diagnose cancer. A definite diagnosis is needed through further chest CT, X-ray, sputum cell examination, etc., and even a perfect pathological biopsy is needed to finally confirm the diagnosis. If the NSE index indicates abnormality during physical examination, it should be treated rationally and scientifically, and patients are recommended to visit oncology department in time and consult professional doctors for further identification.