chromogranin A
Summary
Chromogranin A is an acidic glycoprotein stored in dense-core secretory granules of neuroendocrine cells and is the most specific serum and IHC marker for neuroendocrine tumors. Classic associations: carcinoid, pheochromocytoma, small cell lung cancer.
Detail
Chromogranin A is co-released with peptide hormones (e.g., catecholamines, insulin, glucagon) from dense-core granules, making it a global marker of neuroendocrine secretion. As a tumor marker, elevated serum chromogranin A is used to diagnose and monitor carcinoid tumors, pheochromocytoma/paraganglioma, neuroblastoma, medullary thyroid carcinoma, and small cell lung carcinoma; levels also correlate with tumor burden. PPI use and renal failure can falsely elevate it. By IHC, it stains dense-core granules and is part of the canonical neuroendocrine panel with synaptophysin (membrane of small synaptic-like vesicles), NSE, and CD56. Cleaved peptides like vasostatin and pancreastatin have autocrine effects. Boards classic: episodic hypertension + headache + diaphoresis + elevated chromogranin A = pheochromocytoma.
Sources
- First Aid for USMLE Step 1 2024
- Robbins Basic Pathology 10th ed
- Pathoma
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