- Normally adrenal medulla secretes 80% epinephrine and 20% norepinephrine.
- In adrenal pheochromocytoma mainly epinephrine is secreted, in extra adrenal norepinephrine is secreted exclusively.
- Malignant pheochromocytoma secretes epinephrine, norepinephrine and dopamine.
- Pheochromocytomas roughly follow the 10% rule: 10% are malignant, 10% are extra-adrenal, 10% are bilateral, and 10% are familial.
Associations -90% are sporadic. 10% are part of a hereditary cancer syndrome eg MEN2a and 2b, neurofibromatosis, von Hippel-Lindau syndrome.
Pheochromocytomas is a highly vascular tumor that is why FNAC is not done in this case. (LQ)
- M.C. manifestation of pheochromocytoma
- 60% of the patients have sustained hypertension
- 40% have paroxysmal hypertension
- Arrhythmia, Sinus tachycardia, or Sinus bradycardia
- Angina and myocardial infarction even in the absence of coronary artery disease.
- Profuse sweating (LQ 2012)
- Mild to moderate Weight loss
- Impaired carbohydrate tolerance
- Orthostatic hypotension
- Hypercalcemia, Abdominal pain
- Increase hematocrit
Extra Edge: Wheezing is not a feature.
Extra Edge: Headache, palpitation & sweating are the classic triad of pheochromocytomas (LQ 2012)
Extra Edge: Symptoms may be precipitated by straining, exercise, stress, pressure on the abdomen, surgery, or parturition-or by agents such as beta-blockers, IV contrast agents, or the tricyclic (MCQ)
- Heart failure
- Dilated cardiomyopathy
- Death due to hypertensive crisis.
Diagnosis of pheochromocytoma :
- Screening test: phentolamine test (MCQ):
- The diagnosis of pheochromocytoma is established by the demonstration of increased production of catecholamine or catecholamine metabolites (VMA or the metanephrine).
- Urinary total metanephrine: Most sensitive & specific screening test for pheochromocytoma (LQ 2012)
- Urinary VMA measurements: Less sensitive and specific than urinary metanephrine measurements.
- Urinary catecholamines
- Localization: Abdominal CT/MRI, or meta-iodobenzylguanidine (MIBG-Chromaffin-seeking isotope) scan: 111In somatostatin analogue or 18F-dopa PET scan useful for detection of extra-adrenal tumours.
Extra Edge : For localization of tumour, contrast CT/MRI and MIBG scintigraphy is used
- Alpha & Beta -blockade pre-op: phenoxybenzamine (alpha-blocker) is used before beta -blocker to avoid crisis from unopposed alpha -adrenergic stimulation.
- Surgery to Remove the tumour most common post operative complication is hypotension which is treated by normal saline infusion.
- Beta blocker alone are contraindicated in pheochromocytomas (AIPG 06)
- Most common post operative complication is Hypotension which is managed by giving normal saline.
Treatment of malignant pheochromocytoma
- Aver-Buchâ€™s chemotherapy protocol includes dacarbazine, cyclophosphamide and vincristine.
- 131I MIBG treatment using 200-mCi doses at monthly interval.