NSE, also known as neuron-specific enolase, is an acidic protease specific to neurons and neuroendocrine cells, which is highly expressed in neuroendocrine tumors and can be used for tumor screening, differential diagnosis of tumors, monitoring of disease, evaluation of treatment effects, and early warning of recurrence. Currently, neuron-specific enolase is mainly used for screening and forewarning of the following tumors. In small cell lung cancer, the level of NSE in patients will be significantly higher than in other types of lung cancer, like adenocarcinoma, squamous carcinoma, large cell carcinoma and other non-small cell lung cancers. In neuroblastoma, the expression of neuron-specific enolase is significantly higher than in nephroblastoma, contributing to the diagnosis of both diseases. In other neuroendocrine tumors, like pheochromocytoma, islet cell tumor, medullary thyroid carcinoma, melanoma and retinoblastoma, serum NSE can also be elevated in patients.