Pheochromocytomas are of variable size, ranging from 1 cm to several kilograms, but are normally between 50 to 200 mg. In sporadic pheochromocytomas, even though tabulated, the tumor is actually a single neoplasm. In contrast, familial tumors are often bilateral and usually multicentric.45 In MEN 2 syndromes, even though synchronous bilateral pheochromocytomas may not be present, the adrenal medulla is hyperplastic and is thought to represent pretumor change analogous to C-cell hyperplasia and medullary thyroid carcinoma. Fed by a rich blood supply, pheochromocytomas often have a purplish gray hue when resected and frequently show demarcated areas of cystic necrosis.

As stated previously, nearly 90% of pheochromocytomas are located within the adrenal glands. The remaining 10% to 15% are found from the neck to the bladder, typically along the course of the sympathetic chain. The most frequent extra-adrenal site is at the aortic bifurcation, the so-called organ of Zuckerkandl. Nearly 98% of pheochromocytomas are located in the abdomen, but they can be found in the neck, mediastinum, intracardiac area, or along the sympathetic chain in the chest. Extra-adrenal tumors are more frequently malignant, approximately 40% in our experience.46,47

There is consensus agreement that histopathology, even including intratumoral capsular and vascular invasion or

FIGURE 71-9. A, Posterior view of metaiodobenzylguanidine scan demonstrating an obvious, single, left adrenal pheochromocytoma. B, The gross tumor shows that the adrenal vein has been split down into the tumor capsule, and the bulging tumor can be seen pouting out through the cut end of the adrenal vein. There was no sign of malignancy in this patient, and catecholamines and metanephrines returned to normal postoperatively.

marked cellular pleomorphism, is unreliable to predict malignancy in pheochromocytomas (Fig. 71-9).44 4849 However, in a review of 184 patients with pheochromocytomas and paragangliomas, approximately one third each had diploid, tetraploid, and aneuploid patterns on flow cytometric nuclear DNA analysis. None of the diploid tumor patients died of disease, and the only disease recurrence was a new, primary contralateral intra-adrenal tumor in a patient with MEN 2 syndrome who was subsequently cured following adrenalectomy.50

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