ihcDirect® Chromogranin A (CgA) is a polyHRP conjugated rabbit monoclonal antibody (clone R1004). Chromogranin A (CgA) weights 43 kDa and belongs to the granin family of acidic proteins that constitute a major component of secretory granules of various endocrine and neuroendocrine cells. CgA is present in neuroendocrine cells throughout the body, including the neuroendocrine cells of the large and small intestine, adrenal medulla and pancreatic islets. It is an excellent marker for carcinoid tumors, phenochromocytomas, paragangliomas, and other neuroendocrine tumors. CgA is detected in most cases of small cell and the large majority of neuronal tumors, but not in glial tumors.