Transformation of a Nonfunctional Paraganglioma With I-123 MIBG Scintigraphy Correlation: A Case Report.

A 35-year-old woman presenting with abdominal pain was found to have mildly elevated catecholamine levels and a retroperitoneal mass. The patient underwent a negative I-123 MIBG scintigraphy scan and a nondiagnostic fine needle aspiration. Eleven years later the patient presented with a hypertensive emergency and markedly elevated catecholamine levels. A subsequent I-123 MIBG scintigraphy scan showed intense uptake corresponding to the previously seen retroperitoneal mass. The patient underwent surgical resection and pathology confirmed the presence of a paraganglioma. A paraganglioma is an extra-adrenal pheochromocytoma that contains chromaffin cells and is thus capable of producing catecholamines. I-123 metaiodobenzylguanidine (MIBG) scintigraphy has become the imaging study of choice for paragangliomas and has a sensitivity of ∼77% to 100% in detecting functional paragangliomas. This case demonstrates scintigraphic correlation of the functional transformation of a nonfunctional paraganglioma in a time span of ∼10 years. Although there are previously published case reports of scintigraphic positive, nonfunctional paragangliomas and scintigraphic negative chromaffin cell tumors, there has been no prior documented case of scintigraphic transformation on MIBG.