Neuron-specific enolase, an enzyme involved in the glycolytic pathway, is generally found in neural and neuroendocrine tissues, with the highest activity in brain cells, intermediate activity in peripheral nerve and neurosecretory tissues, and the lowest activity in some non-neural tissues, so that the diagnosis of the disease can be clarified based on the changes in this index, as well as the prognosis. The first one is that the blood level of small cell lung cancer is higher than that of the other. The first is a significant increase in serum neuron-specific enolase in small cell lung cancer. Small cell lung cancer is one of the lung tumors with a relatively poor prognosis, and if the disease is detected early, early treatment is necessary to improve the prognosis. Therefore, small cell lung cancer is highly suspected if there is an increase in the index. Second, in children, neuroblastoma, rhabdomyosarcoma, or Wilms’ tumor (nephroblastoma) is highly suspected, and current research suggests that neuron-specific enolase activity is abnormally high in neuroblastoma, which can be used for differential diagnosis. Of course, the elevation of serum NSE is not clinically meaningful, and the diagnosis should be made with the help of other relevant ancillary tests.