Chromogranin A

Chromogranin A is a member of the chromogranin/secretogranin family of neuroendocrine secretory proteins. Examples of cells producing chromogranin A are the adrenal medulla, enterochromaffin-like cells and beta cells of the pancreas. The function of chromogranin A is unknown but it is a precursor to 3 functional peptides: vasostatin, pancreastatin and parastatin. These peptides negatively modulate the neuroendocrine function of the releasing cell (autocrine) or nearby cells (paracrine).

Chromogranin A is an excellent marker for Carcinoid Tumors, Pheochromocytomas, Paragangliomas, and other Neuroendocrine Tumors. Coexpression of chromogranin A and neuron-specific enolase (NSE) is common in neuroendocrine neoplasms. It has been identified in a wide variety of endocrine tissues including the pituitary, pancreas, hypothalamus, thymus, thyroid, intestine and parathyroid. It is generally accepted that the coexpression of certain keratins and chromogranin means neuroendocrine lineage. The presence of strong chromogranin staining and absence of keratin staining should raise the possibility of paraganglioma. Most pituitary adenomas and prolactinomas readily express chromogranin.

Chromogranin A is a mouse monoclonal antibody derived from cell culture supernatant that is concentrated, dialyzed, filter sterilized and diluted in buffer pH 7.5, containing BSA and sodium azide as a preservative.

1. Fischer-Colbrie R, et al. Neuroscience. 1985;16:547
2. Hearn SA, J Histochem Cytochem. 1987;35:795-801
3. O’Connor DT, et al. Live Sciences. 1986;33:1657-1663
4. Wilson BS, et al. Am J Pathol. 1984;115:458-468

1. Cut and mount 3-4 micron formalin-fixed paraffin-embedded tissues on positive charged slides.
2. Air dry for 2 hours at 58° C.
3. Deparaffinize, dehydrate and rehydrate tissues.
4. Subject tissues to heat epitope retrieval using a suitable retrieval solution such as ImmunoDNA Retriever with Citrate (BSB 0020-BSB 0023) or EDTA (BSB 0030-BSB 0033).
5. Any of three heating methods may be used:
   • Electric Pressure Cooker
     Place standoff rack at base of pressure cooker. Add 1-2 inches of distilled water to the pressure cooker and turn heat to high, and incubate for 15 minutes. Open and immediately transfer slides to room temperature.
   • Water Bath Method
     Place tissues/slides in a pre-warmed staining dish or coplin jar containing the ImmunoDNA Retriever with Citrate or EDTA in a water bath set at 95°-99° C. Incubate for 30-60 minutes.
   • Conventional Steamer Method
     Place tissues/slides in a pre-warmed staining dish or coplin jar containing the ImmunoDNA Retriever with Citrate or EDTA in a Steamer, cover and steam for 30-60 minutes.
6. After heat treatment, transfer slides in ImmunoDNA Retriever with Citrate or EDTA to room temperature and let stand for 15-20 minutes.
7. Wash slides with IHC wash buffer or DI water.
8. Continue IHC staining protocol.