Chromogranin A (CgA) is considered as a major specific neuroendocrine tumor marker. It belongs to the secretogranin family, which is present in the gastrointestinal tract, respiratory system, endocrine glands and in a group of endocrine cells such us pancreas and thyroid. Serum levels of CgA could reflect the neuroendocrine activity and could be used when evaluating advance prostate carcinoma. Moreover, there are also several factors that may increase the serum level of CgA: treatment with proton-pump inhibitors or H2-receptor blockers, chronic atrophic gastritis, rheumatoid arthritis, liver and renal failure. Another method to evaluate NE differentiation is scintigraphy with the 111In-labeled somatostatin analogue (DTPA-D-Phe)-octrotide, (Octreoscan). This method takes advantage of the overexpression of type II somatostatin receptors on the cell surface of NE tumors. With this technique the presence of NE differentiation can be detected both at the primary (prostate) and the metastatic sites. A more specific system to detect NE cell activity is obtained by analyzing CgA gene expression in prostate tissue by a semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR).