Immunohistochemical localization of chromogranin A in endocrine tissues and endocrine tumors of dogs.

Chromogranin A is present in the secretory granules of endocrine cells and functions in hormone packaging, secretory granule stabilization, and regulation of hormone secretion. Immunohistochemical identification of chromogranin A can facilitate diagnosis of endocrine neoplasia. Normal and neoplastic canine tissues were stained immunohistochemically for chromogranin A. Staining of normal endocrine tissues demonstrated chromogranin A in chromaffin cells of the adrenal medulla, C cells of the thyroid gland, and pancreatic islets. The parathyroid chief cells and anterior pituitary stained lightly positive for chromogranin A. Pheochromocytomas (7/7), chemodectomas (5/7), islet cell carcinomas (2/6), pituitary adenomas (4/6), parathyroid adenomas (3/7), and a C-cell carcinoma (1/1) stained positive for chromogranin A. The data indicate that chromogranin A is widely distributed in canine endocrine tissues, and immunohistochemical staining of chromogranin A can be used to confirm the presence of secretory granules in endocrine tumors.