FDG-PET - A SENSITIVE TOOL FOR THE LOCALIZATION OF MIBG-NEGATIVE PELVIC PHEOCHROMOCYTOMAS

Pheochromocytomas are catecholamine-secreting tumors arising from the adrenal medulla or rarely from other structures derived from neurocres t origin. Because biochemical evidence of catecholamine production usu ally precedes clinical manifestations, patients who have undergone res ection of a pheochromocytoma are followed with serial monitoring of ca techolamines. If urinary catecholamines are elevated, localization of recurrent and/or metastatic lesions is obtained by imaging procedures. Computed tomography and magnetic resonance imaging are useful techniq ues, but they do not provide specific metabolic information. Scintigra phy with metaiodobenzylguanidine (MIBG) labeled with either I-123 Or I -131 is recommended for detection of metabolically active pheochromocy tomas [1]. However, a subset of these tumors are MIBG-negative. The F- 18-fluorodeoxyglucose positron emission tomography (FDG-PET) method ha s proven useful in the localization of neoplasms. The use of PET with both FDG and Rb-82 (Rubidium) has been described in the localization o f MIBG-negative suprarenal and thoracic pheochromocytomas [2, 3]. We r eport the utility of FDG-PET to detect pelvic recurrence of pheochromo cytoma in an MIBG-negative patient.