Scintigraphic Localization of Pheochromocytoma

TLDR

The radiopharmaceutical [131I]MIBG accumulates in adrenergic vesicles, allowing retention in pheochromocytomas for days. We administered [131I]MIBG to eight patients and obtained scintigraphic images to localize pheochromocytomas. Scintigraphy with [131I]MIBG identified pheochromocytomas of varied size, location, and hormone secretion—including lesions missed by CT—and guided successful reoperation, demonstrating its safe and reliable localization capability.

Abstract

We used a new radiopharmaceutical agent, [131I]meta-iodobenzylguanidine ([131I]MIBG), to produce scintigraphic images of pheochromocytomas in eight patients. One day or more after injection, the only normal organ that displayed distinct concentrations of radioactivity was the urinary bladder. The [131I]MIBG was probably concentrated in adrenergic vesicles; in tissues where vesicles are numerous, such as pheochromocytomas, the radionuclide was retained for days. The spectrum of pheochromocytomas shown the scintigrams was broad: intra-adrenal and extraadrenal in location, benign and malignant in character, 0.2 to 65 g in weight, and with different hormone patterns in secretion. Tumors in four patients were not detected by computed tomography. In one patient, reoperation was undertaken only because the scintigram located the extra-adrenal tumors and thereby directed the surgeon's exploration. The method offers hope of safe and reliable localization of pheochromocytomas in their many guises.