Biomarkers in neuroendocrine neoplasms.

Neuroendocrine tumors are a heterogenous group of rare neoplasms with different morphological features, immunophenotype, molecular profile, and clinical presentation. They can derive from any neuroendocrine cell throughout the body, but the majority of NENs is developed in the gastrointestinal tract. They can be divided into two groups, based on hormone secretion, functioning and non-functioning NENs. The first group is characterised from the secretion of specific substances, defining the clinical manifestations. Functional NENs can be divided into carcinoid tumors, with serotonin overproduction, and functional GEP NEN's (mostly located in pancreas) that may secrete insulin, VIP, gastrin, glucagon or somatostatin. Non-functioning NENs, comprise approximately 85% of NEN's. As these tumors lack specific symptoms, they come to clinical attention later, when they have a large size or metastases. Apart from the specific biomarkers that functional NENs are producing, there are some general markers that are produced from all NENs and play a major role in the diagnosis, prognosis and follow up of these patients. These are chromogranin (CgA), neuron-specific enolase (NSE) and 5-hydroxyindolic acetic acid (5-HIAA).