Endocrine tumors, also referred to as neuroendocrine tumors (NETs), are defined by a common phenotype which is characterized by the expression of general markers (neuron specific enolase, chromogranin, synaptophysin) and hormone secretion products. These tumors may be localized in any part of the body and are generally discovered in non-specific situations, i.e. not immediately suggestive of NETs (tests for inherited predisposition to tumors or for a clinical syndrome caused by abnormal hormone secretion).