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Pheochromocytoma

Adrenal Medulla

  1. Normally adrenal medulla secretes 80% epinephrine and 20% norepinephrine.
  2. In adrenal pheochromocytoma mainly epinephrine is secreted, in extra adrenal norepinephrine is secreted exclusively.
  3. Malignant pheochromocytoma secretes epinephrine, norepinephrine and dopamine.
  4. 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.

 

Extra Edge:

Pheochromocytomas is a highly vascular tumor that is why FNAC is not done in this case. (LQ)

Pheochromocytoma

Symptoms produced

  1. Hypertension
    1. M.C. manifestation of pheochromocytoma
    2. 60% of the patients have sustained hypertension
    3. 40% have paroxysmal hypertension
  2. Arrhythmia, Sinus tachycardia, or Sinus bradycardia
  3. Angina and myocardial infarction even in the absence of coronary artery disease.
  4. Profuse sweating (LQ 2012)
  5. Mild to moderate Weight loss
  6. Impaired carbohydrate tolerance
  7. Orthostatic hypotension
  8. Hypercalcemia, Abdominal pain
  9. 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)

 

Complications:

  1. Heart failure            
  2. Dilated cardiomyopathy
  3. Arrhythmias             
  4. Stroke         
  5. Death due to hypertensive crisis.   

Diagnosis of pheochromocytoma :

  1. Screening test: phentolamine test (MCQ): 
  2. The diagnosis of pheochromocytoma is established by the demonstration of increased production of catecholamine or catecholamine metabolites (VMA or the metanephrine).
     
    The diagnosis can usually be made by analysis of a single 24 h urine sample.
    1. Urinary total metanephrine:  Most sensitive & specific screening test for pheochromocytoma (LQ 2012)
    2. Urinary VMA measurements:  Less sensitive and specific than urinary metanephrine measurements.
    3. Urinary catecholamines
  3. 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.

Table - Biochemical and Imaging Methods Used for Pheochromocytoma and Paraganglioma Diagnosis (Ref. Hari. 18th ed., Page - 2963, Table 343.2)

 

 

Diagnostic Method

Sensitivity

Specificity

1. 24-h urinary tests

 

 

a. Vanillylmandelic acid

++

++++

b. Catecholamines

+++

+++

c. Fractionated metanephrines

++++

++

d. Total metanephrines

+++

++++

2. Plasma tests

 

 

a. Catecholamines

+++

++

b. Free metanephrines

++++

+++

c. Chromogranin A

+++

++

3. CT

++++

+++

4. MRI

++++

+++

5. MIBG scintigraphy

+++

++++

6. Somatostatin receptor scintigraphy

++

++

7. Dopa (dopamine) PET (preliminary data)

++++

++++


Extra Edge : For localization of tumour, contrast CT/MRI and MIBG scintigraphy is used
 

Treatment

  1. Alpha & Beta -blockade pre-op: phenoxybenzamine (alpha-blocker) is used before beta -blocker to avoid crisis from unopposed alpha -adrenergic stimulation.
  2. Surgery to Remove the tumour most common post operative complication is hypotension which is treated by normal saline infusion. 

Extra Edge:

  1. Beta blocker alone are contraindicated in pheochromocytomas (AIPG 06)
  2. Most common post operative complication is Hypotension which is managed by giving normal saline. 

Treatment of malignant pheochromocytoma

  1. Aver-Buch’s chemotherapy protocol includes dacarbazine, cyclophosphamide and vincristine.
  2. 131I MIBG treatment using 200-mCi doses at monthly interval.




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