False-Positive 123I-Metaiodobenzylguanidine (MIBG) Scan in a Patient with Angiomyolipoma; Positive MIBG Scan does not Necessarily Indicate the Presence of Pheochromocytoma

123I-Metaiodobenzylguanidine (123I-MIBG)-accumulation in angiomyolipoma (AML) is demonstrated. A 24-year-old Japanese woman presented with tumors in the right retroperitoneal space. The tumors, which accumulated 123I-MIBG, had been thought to be adrenal pheochromocytoma before surgery. They were removed, and were found to be AML. 123I-MIBG was accumulated in AML. 123I-MIBG-accumulation in AML led to a false-positive diagnosis of adrenal pheochromocytoma. Cathecholamine levels had been normal. No chromograffin cells were found in the histological examination of the tumors. MIBG accumulation does not necessarily indicate the presence of pheochromocytoma.