Neuron-specific enolase (NSE)

Neuron-specific enolase is an enzyme normally found inside neurons and in neuroendocrine cells (cells with both nerve- and hormone-like features scattered through the body). When cancers arising from these cell types grow, NSE can be released into the blood, so its level tends to reflect the amount of active disease. Its main clinical use is in small-cell lung cancer, an aggressive lung tumour of neuroendocrine origin, and in some neuroendocrine tumours and neuroblastoma in children. In someone with one of these known cancers, NSE is followed over time: a falling level suggests treatment is working, while a rising trend can be an early clue that the disease is becoming more active, prompting closer assessment. It is not used to screen the general population or to make a diagnosis on its own, because it is not specific — modest rises occur in some benign conditions, and blood samples must be handled carefully because red blood cells also contain the enzyme and can falsely raise the result if the sample breaks down. It is interpreted by the specialist team as part of a broader picture.

• Small-cell lung cancer — the main use; higher levels reflect more active disease and are followed during treatment.
• Neuroendocrine tumours — including neuroblastoma in children.
• A rising trend in known disease — can signal the cancer becoming more active.
• Sample handling (haemolysis) — a broken-down blood sample can falsely raise NSE, since red cells contain the enzyme.
• Some benign or neurological conditions — occasional modest, non-cancer rises.

• Normal or low — the expected result, and reassuring during monitoring.
• A falling level during treatment — suggests the therapy is working.
• Not a rule-out — a normal NSE does not exclude cancer.