Pheochromocytomas1 Flashcards
From which cells the pheochromocytomas most commonly arise?
90 % arise from chromaffin cells of the adrenal medulla
What are the paragangliomas and what % of pheochromocytomas arise from them?
10%, arise from extraadrenal chromaffin tissue, found in the paraaortic sympathetic chain, the organ of Zuckerkandl at the origin of the inferior mesenteric artery, the sympathetic chain in the neck or mediastinum, and the wall of the urinary bladder.ﾠ
What percentage of pheochromocytomas could be bilateral and extraadrenal?
More than 10%
What is the clinical triad of pheochromocytomas?
Headache, sweating, and palpitations
Which familial syndromes are associated with pheochromocytomas and what is the associated gene?
von HippelﾖLindau (VHL) syndrome, caused by theﾠVHLﾠgene; multiple endocrine neoplasia type 2 (MEN2), related to theﾠRETﾠprotooncogene; neurofibromatosis type 1 (NF1), associated with theﾠNF1ﾠgene; and familial paraganglioma/pheochromocytoma syndrome, recently linked to the genes encoding subunits B, C, and D of mitochondrial succinate dehydrogenase (SDHB, SDHC,ﾠandﾠSDHD).
Compared to sporadic pheochromocytomas, hereditary pheochromocytomas are?
Multiple, bilateral and/or extraadrenal; are rarely malignant; and generally present at an earlier age.
Which foods and medications can caused false-positive elevations of plasma metanephrines?
Foods ﾖ Cheese, Bananas, Wine, Soy sauce, Avocados, Fermented, smoked, or aged meat and fish
Drugs Used in Obesity Management ﾖ phentermine, Phendimetrazine, Phenylethylamine, Sibutramine
Over-the-Counter Drugs ﾖ Pseudoephedrine, Acetaminophen, Antidepressants, Amitriptyline, Nortriptyline, Reboxetine, Duloxetine, Venlafaxine
Antibiotics ﾖ Linezolid Antiemetics ﾖ Metoclopramide, Chlorpromazine, Prochlorperazine
Which medications have been sucesfully used for preoperative adrenergic blockade in patients with pheochromocytoma?
?-adrenergic antagonists, dihydropyridine calcium channel blockers, the competitive ?- and ?-receptor blocker labetalol, and metyrosine
Which adrenergic blockade medications do not cause rebound tachycardia on patients with pheochromocytoma?
Selective ?1-adrenergic antagonists such as prazosin, doxazosin, and terazosin
Why ?- blockade should not be initiated before first documenting the efficacy of ?-blockade in patient with pheochromocytoma?
Because a hypertensive crisis may ensue from unopposed ?-adrenergic stimulation. This could lead to left-heart strain and congestive heart failure.
What procedure can you try on patients with bilateral pheochromocytoma or metachronous contralateral pheochromocytoma after previous unilateral adrenalectomy?
Unilateral cortex-sparing adrenalectomy and contralateral total adrenalectomy by an open approach or cortex-sparing procedure
What is needed for the diagnosis of malignant pheochromocytoma?
A diagnosis of malignant pheochromocytoma requires documentation of local invasion, recurrence, or metastasis, with the most common sites of metastasis being the liver, lung, bone, and retroperitoneal lymph nodes.
What percentage of pheochromocytomas are malignant?
15%
What treatment can be given to a patient with unresectable malignant pheochromocytoma or paraganglioma?
131 I-MIBG has been shown to produce partial, temporary responses in approximately 1/3 of patients. Patients are treated withﾠ131I-MIBG for 3 to 6 months, with reevaluation including biochemical analysis and MIBG imaging performed prior to each treatment. In patients with poor MIBG uptake or a poor response to MIBG therapy, cytotoxic chemotherapy can be used alone or in combination with MIBG and may have a therapeutic benefit in up to 65% of patients. The most common regimen is a combination of cyclophosphamide, vincristine, and dacarbazine.
