Major related tumors: small cell lung cancer. Other related tumors: lung adenocarcinoma, large cell lung cancer, neuroendocrine carcinoma. Other influencing factors: NSE can be elevated if hemolysis occurs or if the cells are destroyed by prolonged post-collection stasis in separating plasma serum or improper centrifugation. NSE is considered the marker of choice for monitoring small cell lung cancer and is elevated in 60-80% of patients with small cell lung cancer. In remission, 80-96% of patients have normal NSE levels, and if NSE is elevated, it suggests recurrence. Within 24-72 hours after the first round of chemotherapy in patients with small cell lung cancer, NSE is transiently elevated due to the breakdown of tumor cells. Therefore, NSE is an effective marker for monitoring the efficacy and course of small cell lung cancer and can provide valuable prognostic information. NSE can also be used as a marker for neuroblastoma and has high clinical application for the early diagnosis of this disease. Patients with neuroblastoma also have elevated urinary NSE levels, and serum NSE levels decrease to normal after treatment. The measurement of serum NSE levels is an important reference value for monitoring the efficacy of neuroblastoma and predicting recurrence, and is more meaningful than the measurement of urinary catecholamine metabolites. It is also important for the diagnosis of amine precursor uptake decarboxylation cell tumors, seminoma and other brain tumors.