Neuron-Specific Enolase (NSE), also known as Enolase 2 (ENO2), is one of three enolase enzymes found in mammals, and acts as a phosphopyruvate hydratase. NSE is an enzyme that catalyzes the conversion of 2-phosphoglycerate to phosphoenolpyruvate in the glycolytic pathway, and the reverse reaction in gluconeogenesis. NSE has a high stability in biological fluids and can easily diffuse to the extracellular medium and cerebrospinal fluid (CSF) when neuronal membranes are injured.This mammalian glycolytic isoenzyme is located specifically in neurons of neuroendocrine cells, as well as tumors associated with those neurons; however, it has also been detected immunohistochemically in non-neoplastic cells of the pituitary, peptide-secreting tissues, pinealocytes, neuroendocrine cells of the lung, thyroid, parafollicular cells, adrenal medulla, islets of Langerhans, Merkel cells of the skin, and melanocytes. NSE is also a useful marker for identifying normal striated muscle, hepatocytes, and peripheral nerves. Anti-NSE may detect for neuroendocrine differentiation, only when used in a panel of antibodies including more specific markers such as synaptophysin, chromogranin, and neurofilament.