The Chromogranin A test is a blood test that measures the level of CgA, an acidic glycoprotein stored in the secretory granules of neuroendocrine cells throughout the body and released into the bloodstream alongside peptide hormones and biogenic amines during neuroendocrine cell activation or tumour-related hypersecretion. CgA is produced by a wide variety of neuroendocrine cells distributed across the gastrointestinal tract, pancreas, adrenal medulla, thyroid C cells, pituitary gland, lung, and prostate, making it the most broadly applicable and widely used general neuroendocrine tumour marker in clinical oncology practice.
Neuroendocrine tumours, commonly abbreviated as NETs, are a heterogeneous group of neoplasms arising from neuroendocrine cells that can occur at virtually any anatomical site but most commonly originate in the gastrointestinal tract including the small intestine, appendix, rectum, and stomach, the pancreas, and the lung. NETs range from well-differentiated, slow-growing, functionally active tumours that produce hormonal syndromes to poorly differentiated, highly aggressive neuroendocrine carcinomas with rapid clinical progression. CgA is elevated in the majority of NETs regardless of their site of origin, hormonal activity, or degree of differentiation, making it the single most sensitive and clinically useful general marker across the entire spectrum of neuroendocrine neoplasia.
In India, neuroendocrine tumours are increasingly diagnosed as awareness grows among clinicians and diagnostic access to CgA testing and cross-sectional imaging improves. Historically underdiagnosed due to their often indolent presentation and the non-specific nature of early symptoms, NETs are now recognised as a significant oncological challenge requiring specialist multidisciplinary management. The test is performed on a small blood sample drawn from a vein and completed in under five minutes.