False positive metaiodobenzylguanidine scan in a patient with a huge adrenocortical carcinoma.

We report a case of a 17-cm cortisol-secreting adrenocortical carcinoma in which [123I] metaiodobenzylguanidine (MIBG) scan showed accumulation of the isotope in the area of the tumor. Catecholamine levels were normal, and no chromaffin cells were found in histological examination of the tumor. A literature review of previously described cases of false positive MIBG scans in the adrenal region is offered. We conclude that MIBG scans might not be as specific as previously thought in differentiating pheochromocytoma from adrenocortical carcinoma. They should be performed only when clinical suspicion and abnormalities in catecholamines advocate the need.