Pheochromotocytoma is a rare but life-threatening tumor of chromaffin cells characterized by excessive production of catecholamines. Malignant pheochromocytoma is established by the development of distant metastases in non-chromaffin cell sites. The pathogenesis of sporadic pheochromocytomas is largely unknown, and specific genetic markers that distinguish benign from malignant tumors remain unidentified. Extra-adrenal involvement and large tumor size are major features suggestive of future malignant potential. In some cases, increased dopamine excretion and its metabolites are associated with malignant pheochromocytoma. Nuclear imaging techniques, such as metaiodobenzylguanidine (MIBG) scintigraphy, somatostatin receptor scintigraphy, and positron emission tomography (PET) scanning play important roles in localizing metastatic lesions. In selected patients, radical resection of primary and metastatic tumors is the treatment of choice, either with curative or palliative intention. Pharmacological blockade of the effects of catecholamine excess is critical in preoperative care and long-term management of malignant pheochromocytoma. Therapy with iodine (I) 131-MIBG is the treatment of choice when unresectable MIBG-positive lesions are present. The usefulness of yttrium (y) 99-labeled somatostatin analogs is still undergoing study. Chemotherapy is reserved for patients with progressive disease who do not respond to other therapies, and external beam radiation is indicated for patients with local symptoms caused by tumor invasion. Future advances in clinical management of malignant pheochromocytoma depend on the development of specific predictors for malignancy and effective novel treatments.
*Endocrine Fellow and †Attending Physician, Pediatric and Reproductive Endocrinology Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, U.S.A.
CHIEF EDITOR’S NOTE: This article is the 19th of 36 that will be published in 2002 for which a total of up to 36 Category 1 CME credits can be earned. Instructions for how credits can be earned appear after the Table of Contents.
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