NSE, scientifically known as neuron-specific enolase, is a widely used tumor marker in clinical practice. The most important use of NSE is to monitor small cell lung cancer to see whether it is present or not, or how well it works after treatment. The vast majority of patients with small cell lung cancer will have elevated NSE, and if treated effectively, this indicator will generally drop to normal. In addition to small cell lung cancer, other tumors such as neuroendocrine tumors and tumors derived from germ cells may also have elevated NSE, such as neuroblastoma, and seminomatous cell tumors, as well as the relatively rare amine precursor uptake and decarboxylation cell tumors. In conclusion, this is a relatively common tumor marker and is most often used to monitor small cell lung cancer.