CHGA (Chromogranin A) encodes a protein involved in the production of secretory vesicles in endocrine and neuroendocrine cells. Levels of this protein correlate with the number of secretory vesicles present, and staining of this protein is useful for subtyping neuroendocrine tumors in multiple tissues including the lung. Serum of patients with small cell lung cancer can be checked for circulating CHGA, and in this context it has been shown to have more sensitivity than neuroendocrine marker NSE. Sensitivity of CHGA is expected to increase with stage. Staining for Chromogranin A is expected to be cytoplasmic. References: Gut, 2016; Syversen, 2004; Taneja, 2004; Seregni, 2001; Endoc Rev 2011 32:755