Chromogranin A (CgA) is a glycoprotein found in neuroendocrine cells and may be useful as a tumor marker for neuroendocrine tumors. Elevated circulating chromogranin A (CgA) levels are found in neuroendocrine tumors (NETs), but the diagnostic usefulness of this marker is still debatable. Research demonstrates that higher CgA levels associate with metastatic disease, confirming that CgA levels can provide a helpful practical biochemical marker for the clinical management of NETs, but with low sensitivity and specificity.

Human chromogranin A is 439 amino acid protein with a molecular weight of 49 kilodalton. It is a secretory protein that is produced by the dense-core vesicles of neuroendocrine cells.