Pheochromocytoma

Published on 25/03/2015 by admin

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Chapter 574 Pheochromocytoma

Pheochromocytomas, catecholamine-secreting tumors, arise from chromaffin cells. The most common site of origin (approximately 90%) is the adrenal medulla; however, tumors may develop anywhere along the abdominal sympathetic chain and are likely to be located near the aorta at the level of the inferior mesenteric artery or at its bifurcation. They also appear in the peri-adrenal area, urinary bladder or ureteral walls, thoracic cavity, and cervical region. Ten percent occur in children, in whom they present most frequently between 6 and 14 yr of age. Tumors vary from 1 to 10 cm in diameter; they are found more often on the right side than on the left. In more than 20% of affected children, the adrenal tumors are bilateral; in 30-40% of children, tumors are found in both the adrenal and extra-adrenal areas or only in an extra-adrenal area.

Pheochromocytomas may be associated with genetic syndromes such as von Hippel-Lindau disease, as a component of multiple endocrine neoplasia (MEN) syndromes MEN-2A and MEN-2B, and more rarely in association with neurofibromatosis. The classic features of von Hippel–Landau syndrome, which occurs in 1 : 36,000 individuals, include retinal and central nervous system hemangioblastomas, renal clear cell carcinomas and pheochromocytomas, but kindreds differ in their propensity to develop pheochromocytoma; in some kindreds, pheochromocytoma is the only tumor to develop. Germline mutations in the VHL tumor suppressor gene on chromosome 3p25-26 have been identified patients with this syndrome. Mutations of the RET proto-oncogene on chromosome 10 (10q11.2) have been found in families with MEN-2A and MEN-2B. Patients with MEN-2 are at risk of developing medullary thyroid carcinoma and parathyroid tumors; approximately 50% develop pheochromocytoma, with patients carrying mutations at codon 634 of the RET gene being at particularly high risk. Mutations are present in the NF1 gene on chromosome 17q11.2 in neurofibromatosis patients.

Pheochromocytomas may occur in kindreds along with paragangliomas, particularly at sites in the head and neck. Such families typically carry mutations in the SDHB, SDHD, and rarely the SDHC genes encoding subunits of the mitochondrial enzyme, succinate dehydrogenase.

Pheochromocytomas are also associated with tuberous sclerosis, Sturge-Weber syndrome, and ataxia-telangiectasia. Somatic mutations of the genes mentioned above, particularly VHL, have been found in some sporadic cases of pheochromocytoma (Chapter 589).

Clinical Manifestations

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