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- A pheochromocytoma is a rare neuroendocrine tumor arising from the adrenal or extra-adrenal chromaffin tissue and, less commonly, the sympathetic ganglia.
- These tumors are catecholamine-producing: norepinephrine (NE) > epinephrine (EPI) > dopamine.
- System(s) affected: endocrine; nervous; cardiovascular
- Synonym(s): chromaffin tumors; paragangliomas
- 500 to 1,000 cases per year were diagnosed in the United States.
- <0.2% of people with severe hypertension (HTN)
Affects all genders and ages; usually diagnosed in 4th to 5th decades of life, familial cases diagnosed 1 decade earlier
Etiology and Pathophysiology
Pheochromocytoma is a tumor that releases catecholamines into the circulation. Catecholamines bind to adrenergic receptors to produce various effects that could induce severe or lethal cardiovascular and cerebrovascular complications.
- Stimulation of α1 receptors (NE > EPI) causes smooth muscle constriction resulting in high BP (arteriolar vasoconstriction).
- Stimulation of α2 receptors (EPI > NE) causes smooth muscle contraction, cardiac muscle relaxation, and inhibition of hormones, such as insulin, resulting in elevated blood glucose (BG) levels.
- Stimulation of β1 receptors (EPI = NE) causes heart muscle contraction resulting in increased heart rate.
- Stimulation of β2 receptors (EPI > NE) causes smooth muscle relaxation.
- In 80% of cases, it is a sporadic disease of unknown etiology.
- In 20% of cases, it has familial origin and is a component of one of the following four autosomal dominant diseases.
- Multiple endocrine neoplasia type 2 (MEN-2)
- von Hippel-Lindau syndrome (VHL)
- Hereditary paraganglioma (PGL) syndrome
- Neurofibromatosis type 1 (NF1)
- Tumor location
- 80% are solitary and unilateral.
- 20% are divided between bilateral lesions and extra-adrenal masses (organ of Zuckerkandl, neck, mediastinum, abdomen, pelvis).
Genetic testing is recommended; genes are identified in the pathogenesis.
- Rearranged during transfection (RET) proto-oncogene
- von Hippel-Lindau disease tumor suppressor gene (VHL)
- NF1 tumor suppressor gene (NH-1)
- Genes encoding four succinate dehydrogenase (SDH) complex subunits
- Gene encoding the enzyme responsible for flavination of the SDHA subunit
- Tumor suppressor TMEM127 gene
- Familial pheochromocytoma
- Familial paraganglioma
- VHL disease
- von Recklinghausen NF1
Commonly Associated Conditions
- MEN-2A (medullary thyroid carcinoma and primary hyperparathyroidism)
- MEN-2B (medullary thyroid carcinoma and mucosal neuromas)
- VHL disease (retinal angiomas, cerebellar hemangioblastomas, renal cysts, carcinomas, pancreatic cysts, epididymal cystadenomas)
- Sturge-Weber syndrome
- Tuberous sclerosis
- Carney syndrome (gastric epithelioid leiomyosarcoma, pulmonary chondroma, extra-adrenal paraganglioma)
- Familial paraganglioma
- Renal artery stenosis