Posterior Mediastinal Pheochromocytoma

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Radiologic-Pathologic Conferences of
the Massachusetts General Hospital

Posterior Mediastinal Pheochromocytoma

Steven Chao¹, Mark E. Mullins and Priscilla J. Slanetz

^¹ All authors: Department of Radiology, Division of Breast Imaging, ACC 219, Massachusetts General Hospital, 32 Fruit St., Boston, MA 02115.

Received October 2, 2000; accepted after revision December 4, 2000.

From the weekly radiologic-pathologic correlation conferencesconducted by Theresa C. McLoud.

Address correspondence to P. J. Slanetz.

Introduction

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Introduction
References

A 19-year-old man with labile hypertension refractory to pharmacologic treatment,severe headaches, palpitations, diaphoresis, and dizziness underwentchest radiography that showed a rounded opacity along the right heartborder (Fig. 1A). MR imaging revealed a 6 x 6 x 3 cm paravertebralrightsided posterior mediastinal mass centered at T8-T9 witha salt-and-pepper appearance (Fig. 1B) and mild scalloping ofthe vertebral bodies. Measurement of elevated levels of norepinephrine, metanephrines,and vanillylmandelic acid in 24-hr urine collections and single-photonemission computed tomography visualization of intense uptakeof pentetreotide tracer by the mass confirmed the diagnosisof extraadrenal pheochromocytoma. The patient underwent thoracotomyand resection of the posterior mediastinal mass (Fig. 1C). Microscopichistopathology revealed a well-circumscribed encapsulated nodularlesion containing highly vascularized nests of cells. The finalpathologic diagnosis was pheochromocytoma (Fig. 1D).

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Fig. 1A. —19-year-old man with labile hypertension, headaches, palpitations, and diaphoresis. Frontal chest radiograph shows rounded right paraspinal mass.

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Fig. 1B. —19-year-old man with labile hypertension, headaches, palpitations, and diaphoresis. Coronal T1-weighted MR image shows characteristic salt-and-pepper appearance of paraspinal mass, confirming diagnosis of pheochromocytoma.

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Fig. 1C. —19-year-old man with labile hypertension, headaches, palpitations, and diaphoresis. Gross pathology specimen shows well-demarcated nodular right posterior mediastinal mass (seen on A and B). (Reprinted with permission from [5])

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Fig. 1D. —19-year-old man with labile hypertension, headaches, palpitations, and diaphoresis. Photomicrograph of specimen shows round nests of large regular polyhedral cells separated by congested capillaries. Note acellular tumor capsule. Both capillaries and capsule are typical of pheochromocytoma. (H and E, x100)

Pheochromocytomas are vascularized chromaffin cell neoplasmsthat secrete catecholamines and, in some cases, other activepeptides; they are responsible for approximately 0.1-0.5% ofpatients with hypertension [1]. The classic symptoms accompanyinghypertension with pheochromocytoma are headache, palpitation,and excessive sweating. Pheochromocytomas are a curable causeof hypertension but can be fatal if not recognized. In the adultpopulation, 10% are extraadrenal, usually derived from the chromaffincells of the sympathetic ganglia. Most (98%) pheochromocytomasare in the abdomen and are associated with the celiac, superiormesenteric, and inferior mesenteric ganglia. Approximately 1%occur in the thorax. Histopathologically, pheochromocytomashave cells arranged in small clusters separated by prominentfibrovascular stroma.

Elevation of catecholamine levels and their metabolites in 24-hrurine collections is diagnostic of pheochromocytoma if the patientis hypertensive or symptomatic at the time of collection. Althoughunenhanced radiography and CT can localize the tumor, MR imagingis the technique of choice. A recent study found MR imagingto be 88% sensitive, 98% sensitive, and 100% sensitive for thedetection of extraadrenal, unilateral adrenal, and bilateraladrenal lesions, respectively [2]. The salt-and-pepper appearanceof these tumors on MR imaging is characteristic, with the pepperrepresenting flow voids of vessels and the salt representing theT1 bright tumor parenchyma. ¹³¹I-metaiodobenzylguanidine (MIBG),which is concentrated in pheochromocytomas by the amine uptake process,is 85% sensitive and 95% specific for detecting these tumors [3].Other imaging methods such as ¹¹¹In-octreotide scintigraphyand positron emission tomography with ¹⁸F-fluorodeoxyglucose,complement and supplement MIBG imaging. IV contrast materialshould be administered with caution because hypertensive crisiscan be precipitated. Percutaneous fine-needle biopsy is contraindicatedfor similar reasons.

Treatment of isolated benign tumors is surgical; perioperativesurgical mortality is 2-3%. Hypertension and its symptoms generallyresolve after surgery, although some patients require long-termpharmacologic treatment. Five-year survival after surgery isgreater than 95%, and recurrence is less than 10%. Malignancyis determined by metastasis and occurs more frequently in extraadrenalthan in adrenal pheochromocytomas [4].

References

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Introduction
References

Francis IR, Korobkin M. Pheochromocytoma. Radiol Clin North Am 1996;34:1101 -1112[Medline]
Jalil ND, Pattou FN, Combemale F, et al. Effectiveness and limits of preoperative imaging studies for the localisation of pheochromocytomas and paragangliomas. Eur J Surg 1998;164:23 -28[Medline]
Shapiro B, Copp JE, Sisson JC, Eyre PL, Wallis J, Beierwaltes WH. Iodine-131 metaiodobenzylguanidine for the locating of suspected pheochromocytoma: experience in 400 cases. J Nucl Med 1985;26:576 -585[Abstract/Free Full Text]
Whalen RK, Althausen AF, Daniels GH. Extra-adrenal pheochromocytoma. J Urol 1992;147:1 -10[Medline]
Conlin RP, Faquin WC. A 19-year-old man with bouts of hypertension and severe headaches. N Engl J Med 2001;344:1314 -1320[Free Full Text]