Pheochromocytoma and Paraganglioma Treatment (PDQ®): Treatment - Health Professional Information [NCI]-General Information About Pheochromocytoma and Paraganglioma Pheochromocytomas and extra-adrenal paragangliomas are rare tumors arising from neural crest tissue that develops into sympathetic and parasympathetic paraganglia throughout the body.

The most recent World Health Organization classification utilizes the term pheochromocytoma exclusively for tumors arising from the adrenal medulla, and the term extra-adrenal paraganglioma for similar tumors that arise from other locations.[1]

Incidence and Mortality

The incidence of pheochromocytoma is 2 to 8 per million persons per year.[2,3] Pheochromocytoma is present in 0.1% to 1% of patients with hypertension,[4,5,6] and it is present in approximately 5% of patients with incidentally discovered adrenal masses.[7] The peak incidence occurs in the third to fifth decades of life; the average age at diagnosis is 24.9 years in hereditary cases and 43.9 years in sporadic cases.[8] The incidence is equal between males and females.[9]

Anatomy

Pheochromocytomas and extra-adrenal paragangliomas arise from neural crest tissue. Neural crest tissue develops into sympathetic and parasympathetic paraganglia.

Sympathetic paraganglia include the following:

• The adrenal medulla.
• The organ of Zuckerkandl near the aortic bifurcation.
• Other paraganglia along the distribution of the sympathetic nervous system.

Parasympathetic paraganglia include the following:

• The carotid body.
• Other paraganglia along the cervical and thoracic branches of the vagus and glossopharyngeal nerves.

Risk Factors

No known environmental, dietary, or lifestyle risk factors have been linked to the development of pheochromocytoma.

Hereditary Predisposition Syndromes

Of all pheochromocytomas and extra-adrenal paragangliomas, 25% occur in the setting of a hereditary syndrome.[8,9,10] Major genetic syndromes that have been identified as carrying an increased risk of pheochromocytoma are included in Table 1.

Table 1. Major Genetic Syndromes That Carry an Increased Risk of Pheochromocytoma

Genetic Syndrome or Condition	Affected Gene	Comment
Multiple endocrine neoplasia type 2A and 2B	RET	(Refer to thePheochromocytoma section in the PDQ summary on theGenetics of Endocrine and Neuroendocrine Neoplasiasfor more information.)
von Hippel-Lindau disease	VHL
Neurofibromatosis type 1	NF1
Hereditary Paraganglioma Syndrome	SDHD[11]	Formerly referred to as familial pheochromocytoma-paraganglioma syndrome type 1
	SDHAF2(SDH5)[12]	Formerly referred to as familial pheochromocytoma-paraganglioma syndrome type 2
	SDHC[13]	Formerly referred to as familial pheochromocytoma-paraganglioma syndrome type 3
	SDHB[14]	Formerly referred to as familial pheochromocytoma-paraganglioma syndrome type 4
	SDHA[15]

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