Discrepancy between PNMT presence and relative lack of adrenaline production in extra-adrenal pheochromocytoma.

Among catecholamine synthesizing enzymes, phenylethanolamine-N-methyltransferase (PNMT) exists only in adrenal and extra-adrenal pheochromocytoma has been believed not to produce adrenaline. However, adrenaline production is clinically active in some extra-adrenal cases. To investigate this controversy, the localization of catecholamine synthesizing enzymes was studied by immunohistochemical staining in extra-adrenal and adrenal cases. The results showed that PNMT was expressed not only in many cases of adrenal pheochromocytoma, but also in extra-adrenal pheochromocytoma. It is suspected that little adrenaline production in extra-adrenal cases is attributable to a lack of a good environment for the activation of PNMT by a high concentration of glucocorticoids.