The Pathology Dictionary Team
May 10, 2023
Chromogranin is a type of protein found primarily in neuroendocrine cells. There are three chromogranin proteins encoded by the CHGA (chromogranin A), CHGB (chromogranin B), and CHGC (chromogranin C) genes.
Chromogranins play important roles in the regulated secretion of hormones and specialized proteins called neuropeptides. They are present in small intracellular structures called secretory vesicles and are released along with other bioactive substances during a process called exocytosis. Chromogranin A has been identified as a prohormone that can be processed into various biologically active peptides, including vasostatin, pancreastatin, and chromostatin.
In addition to their role in secretory granules, chromogranins have been implicated in other cellular functions, such as calcium binding, protein trafficking, and modulation of immune responses. They are also known to be involved in the pathogenesis of certain diseases, including neuroendocrine tumors, cardiovascular disorders, and autoimmune diseases.
The measurement of chromogranin A levels in the blood is often used as a diagnostic and prognostic marker for neuroendocrine tumors, such as carcinoid tumors and neuroblastomas. Elevated levels of chromogranin A can indicate the presence of these tumors or be used to monitor treatment response. Pathologists use a test called immunohistochemistry (IHC) to look for cells expressing chromogranin in a tissue sample.
Chromogranin expression is predominantly found in neuroendocrine cells, which are specialized cells that release hormones and neurotransmitters. These cells are distributed throughout the body.
Normal cells that express chromogranin include:
Chromogranin expression is frequently observed in tumours made up of neuroendocrine cells. These types of tumours include carcinoid tumours, well differentiated neuroendocrine tumours, poorly differentiated neuroendocrine carcinomas, small cell carcinomas, large cell neuroendocrine carcinomas, medullary thyroid carcinomas, Merkel cell carcinoma, pheochromocytomas, and paragangliomas. Chromogranin can also be expressed by other types of tumours if the cells in the tumour have started to change into neuroendocrine cells. Pathologists often describe this as neuroendocrine differentiation.
Positive means that the cells in the tissue sample were making chromogranin protein.
Negative means that the cells in the tissue sample were not making chromogranin.