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Pheochromocytomas
Introduction
- Very rare tumors (only 3 reported cases).
- Usually unilateral, slow growing adrenal masses.
- Occasionally extra-adrenal.
- May reach a considerable size before clinical signs.
- Signs: often vague - intermittent tachycardia, hypertension.
- Diagnosis: histopathology, hormonal assay.
- Treatment: surgery.
- Prognosis: guarded.
Presenting signs
- Polyuria/polydipsia.
- Intermittent vomiting.
- Depression.
Acute presentation
- Theoretically sudden death due to cardiac arrhythmia.
Age predisposition
- Old (>11 years).
Special risks
- Surgery due to risk of catecholamine release → cardiac arrhythmias when tumor handled.
Pathogenesis
Predisposing factors
General
- Chromaffin cell adrenal tumor or may be derived from extra-adrenal paraganglionic tissue.
- Secrete catecholamines (80% noradrenaline) which → vasoconstriction and hypertension by action on alpha and beta receptors → signs.
- Release often intermittent (may be mediated by changes in tumor blood flow and trauma → intermittent signs.
- May be malignant; if so, may invade caudal vena cava or metastasize to lung, liver or bone
- Occasional incidental post mortem finding.
Pathophysiology
- Signs related to release of catecholamines.
- Secretion of catecholamines is often intermittent and so signs are correspondingly variable and range from subclinical to cardiovascular collapse.
- Signs are related to secretion of catecholamines and their systemic effects:
- Generalized vasoconstriction by stimulation of alpha receptors.
- Positive chronotropic and inotropic effects on the heart.
- Capillary dilation and reduced gastrointestinal motility caused by stimulation of beta2 receptors.
Timecourse
- Weeks to years.
Diagnosis
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Treatment
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Prevention
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Outcomes
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Further Reading
Publications
Refereed papers
- Recent references from PubMed and VetMedResource.
- Daniel G, Mahony O M, Markovich J E et al (2015) Clinical findings, diagnostic and outcome in 33 cats with adrenal neoplasia (2002-2013). J Feline Med Surg 18 (2), 77-84 PubMed.
- Chun R, Jakovijevic S, Morrison W B et al (1998) Apocrine gland adenocarcinoma and pheochromocytoma in a cat. JAAHA 33 (1), 33-36 PubMed.
- Maher E R Jr. (1994) Pheochromocytoma in the dog and cat - diagnosis and management. Sem Vet Surg (Small Animal) 9 (3), 158-166 PubMed.
- Henry C J, Brewer W G Jr., Montgomery R D et al (1993) Clinical vignette. Adrenal Pheochromocytoma. JVIM 7 (3), 199-201 PubMed.
- Patnaik A K, Erlandson R A, Lieberman P H et al (1990) Extra-adrenal pheochromocytoma (paraganglioma) in a cat. JAVMA 197 (1), 104-106 PubMed.