To the Editor.—Recently, iodine-131-metaiodobenzylguanidine, a compound chemically resembling noradrenaline, accumulated in chromaffin tissue as storage granules.1,2 Metaiodobenzylguanidine is an adrenergic neuron blocker, an inhibitor of neuronal uptake, and a presynaptic α2-agonist. The metaiodobenzylguanidine scan is a safe, specific, and noninvasive procedure for the localization of pheochromocytomas3,4; its limit is the possibility of false-negative scans in 10% of patients, whereas computed tomography (CT) visualizes more than 95% of the intra-adrenal tumors.5
Brown and colleagues6 reported a case of a false-positive metaiodobenzylguanidine scan that showed a bilateral adrenal uptake in a patient with a right-sided pheochromocytoma. They concluded that scintigraphy cannot yet replace computed tomography, selected venous sampling, or angiography in the diagnosis of adrenal pheochromocytomas.
Fig 1.—Metaiodobenzylguanidine scan showing area of iodine uptake in the right adrenal gland. MIBEG BKG-SUBTRACT. MIBEG DTPA MIBEG + DTPA
We report the case of a 30-year-old man who presented