Dihydroxyphenylalanine secretion in a malignant pheochromocytoma

Studies on catecholamine metabolism in patients with neural crest tumors revealed a high plasma level of 3,4-dihydroxyphenylalanine (dopa) and dopamine (DM) in association with a malignant, but not a benign pheochromocytoma. The large amounts of these amines may have been mistaken in other studies for norepinephrine because of the use of a methodology of insufficient specificity. This observation may provide a means of differentiating between these two tumors which at present cannot be distinguished histopathologically or biochemically. In respect to urinary catechols, the malignant tumor resembled the neuroblastoma. However, neuroblastoma tissue, unlike both pheochromocytomas, contained a negligible amount of norepinephrine (NE), possibly accounting for the paradoxical absence of cardiovascular symptoms in patients with neuroblastoma despite large amounts of presser urinary catecholamines.