Immunohistochemical Expression of Choline Acetyltransferase and Catecholamine-Synthesizing Enzymes in Head-and-Neck and Thoracoabdominal Paragangliomas and Pheochromocytomas

Paragangliomas (PGLs) are neural-crest-derived, non-epithelial neuroendocrine tumors distributed along the parasympathetic and sympathetic nerves. Head-and-neck PGLs (HNPGLs) have been recognized as nonchromaffin, nonfunctional, parasympathetic tumors. By contrast, thoracoabdominal paragangliomas and pheochromocytomas (PPGLs) are chromaffin, functional, sympathetic tumors. Although HNPGLs and PPGLs have the same histological structure, the zellballen pattern, composed of chief and sustentacular cells surrounded by abundant capillaries, the pathobiological differences between these types of PGLs remain unclarified. To determine the phenotypic features of these PGLs, we performed an immunohistochemical study using specific antibodies against choline acetyltransferase (ChAT), an enzyme involved in acetylcholine synthesis, and enzymes for the catecholamine-synthesis, tyrosine hydroxylase (TH), and dopamine beta-hydroxylase (DBH), in 34 HNPGLs from 31 patients, 12 thoracoabdominal PGLs from 12 patients, and 26 pheochromocytomas from 22 patients. The expression of ChAT, TH, and DBH was 100%, 23%, and 10% in the HNPGLs; 12%, 100%, and 100% in the pheochromocytomas; and 25%, 67%, and 100% in the thoracoabdominal PGLs, respectively. These results designate HNPGLs as acetylcholine-producing parasympathetic tumors, in contrast to PPGLs being catecholamine-producing tumors. The other most frequently used neuroendocrine markers are synaptophysin and chromogranin A expressed 100% and 80%, respectively, and synaptophysin was superior to chromogranin A in HNPGLs. This is the first report of HNPGLs being acetylcholine-producing tumors. Immunohistochemistry of ChAT could be greatly useful for pathologic diagnosis of HNPGL. Whether measurement of acetylcholine levels in the blood or urine could be a tumor marker of HNPGLs should be investigated soon.