Chromogranin

Chromogranin A is a granin protein found in neurosecretory vesicles of neurons and endocrine cells, and its IHC stain serves as a specific, though not highly sensitive marker of neuroendocrine differentiation. In IHC, it highlights neuroendocrine cells and tumours such as carcinoid tumours, pheochromocytoma, neuroendocrine carcinomas, Merkel cell carcinoma, and paraganglioma, typically showing granular cytoplasmic staining corresponding to neurosecretory granules. It is more sensitive in well‑differentiated neuroendocrine tumours and helps distinguish pheochromocytoma (almost always positive) from adrenocortical carcinoma (almost always negative)(1).

Recommended Controls

Criteria for acceptable staining is a granular cytoplasmic staining pattern. The recommended positive control to use for a chromogranin stain is an appendix which is both a positive and negative tissue control. The neuroendocrine cells in appendiceal mucosa should stain intensely positive while the epithelial and smooth muscle cells should have no staining at all. The Langerhans islet cells also stain quite intensely in normal pancreas which is a high expressor of this antigen.

Expected staining pattern

Neuroendocrine tumour

Normal Pancreas

Disclaimer

These methods are intended as a guide only. Laboratories that wish to implement these methods should perform internal validation/verification prior to use. The RCPAQAP does not make any claim or warranty for the accuracy or performance of these methods.