Chromogranin A

Chromogranin A is a very specific marker for neuroendocrine cell differentiation (reacts with cytoplasmic neurosecretory granules). Unfortunately, it is not highly sensitive. It is often used as part of a panel to identify neuroendocrine neoplasms (e.g. synaptophysin, CD56). It is more often positive in well-differentiated lesions, and stains the neurosecretory granules in the cell cytoplasm.

Chromogranin A is expressed in approximately 30% of small cell carcinomas and neuroblastomas.

Photomicrographs

Chromogranin A - Pheochromocytoma — Pheochromocytoma stained with chromogranin A (strong expression).

Chromogranin A - Pancreas Islet Cells — Pancreatic islet cells stained with chromogranin A (strong expression).

Chromogranin A - Merkel Cell Carcinoma — Perinuclear dot-like expression of chromogranin A in Merkel cell carcinoma.

Chromogranin A - Benign Colon — Scattered neuroendocrine cells present in benign colon.

Chromogranin A - Carcinoid — Chromogranin A expression in a carcinoid tumor (strong diffuse)

Reference

Wick, MR. “Immunohistochemical approaches to the diagnosis of undifferentiated malignant tumor.”Annals of Diagnostic Pathology12(2008):72-84.