Chromogranin A (CgA) is an acid glycoprotein with 439 amino acids that is present in the secretory dense core granules of most neuroendocrine cells. The chromogranin family consists of at least three different water-soluble acidic glycoproteins (CgA, CgB, and secretogranin II, sometimes called Chromogranin C).

Upon stimulation, CgA and other peptide hormones and neuropeptides are released. CgA is also secreted from neuroendocrinederived tumors.

Neuroendocrine tumors (NETs), which originate from neuroendocrine cells, are found widely distributed throughout the body. The most common sites of NET are the lung, stomach, appendix, cecum, duodenum, pancreas, jejunum/ileum, colon and rectum. NET arising from the gastrointestinal tract are collectively known as gastroenteropancreatic neuroendocrine tumors (GEP-NET) and account for approximately 2/3 of incident NET. The annual incidence of NET is estimated as 2 – 5 cases per 100,000 population.

CgA is widely expressed throughout the neuroendocrine system and serves as a general biomarker for a wide variety of neuroendocrine tumors. The determination of Chromogranin A helps in the detection of neuroendocrine tumors and is used to assess the course of cancer treatment.