Pheochromocytoma Flashcards
What’ s the signalment for pheochromocytoma?
- older dogs (>11yo)
- no gender or breed predilection
- extremely rare in cats
What are some clinical signs associated with pheochromocytoma?
intermittent episodes of collapse, weakness, and/or panting
- CV: tachycardiac, tachypnea, systemic hypertension, arrhythmia, collapse, pale, hemorrahge
- neuromuscular system: weakness, tremors, seizures, anxiety, pacing
- nonspecific: weight loss, lethargy, anorexia
- Miscellaneous: PU/PD, v/d, abdominal pain
If tumour is quite large:
- tumour invasion of vascular/ thromboembolism
- hemorrhage/ rupture
- metastasis: liver, kidney, spleen, LNs, lungs, heart, bones, and CNS
What are some lab work abnormalities that may be noted with pheochromocytoma?
none specific
- increase in liver value
- increase in hyperglycemia (20%)
- increase in proteinuria (20%) due to hypertensive glomerulopathy or concurrent illness
How often is arterial hypertension noted with pheochromocytoma?
only in 50% of the patients!
What’s the imaging modality of choice for pheochromocytoma?
CT or MRI. Contrast enhancement helps with possible tumour invasion
- in people, use of ionic contrast can induce crisis – not reported in dogs
What’s the utilities of FNA an adrenal mass?
do NOT do it if suspecting pheochromocytoma
- cytology can differentiate location, not malignancy
What biochemistry testing can be done for pheochromocytoma?
urine catecholamine (NMN:creatinine ratio)
- metanephrine, normetanephrine
- drugs may interfere with results
- ex. phenoxybenzamine, steroids –> increase NMN and norepinephrine
Inhibin measurement
- can ddx between pheochromocytoma vs Cushing’s
- undetectable in pheochromocytoma
- can’t be used in intact dogs
What’s the treatment for pheochromocytoma?
Adrenalectomy
What are some pre-op management options to reduce fatal catecholamine release?
too much catecholamine: hypertensive crisis, cardiac arrythmia, pulmonary edema, and cardiac ischemia
- use phenoxybenzamines for alpha blockade
- THEN can use atenolol for beta blockade
What’s the MOA of phenoxybenzamines?
alpha-adrenergic receptor antagonist –> irreversibly binds to alpha 1 and alpha 2 receptors so epinephrine and norepinephrine can’t bind to it
Which IHC can be used to confirm pheochromocytoma?
chromogranin A (only present in chromatin granules from the medulla, not from the cortex)
How reliable is histo for malignancy of pheochromocytoma?
Not reliable. The only reliable indicator of malignancy is metastasis
