Pheochromocytoma Wendy Blount, DVM

Pheochromocytoma Uncommon tumor of the chromaffin cells in the adrenal medulla Occasionally can arise from chromaffin cells outside the adrenal gland Right adrenal more common than left Bilateral has been reported Most are malignant and functional Produce catecholamines Epinephrine Norephinephrine Dopamine (rare)

Pheochromocytoma 40%have metastasized at the time of diagnosis Regional lymph nodes (sublumbar) Liver Lung Bone CNS Many invade the caudal vena cava Sometimes when the tumor is not found on ultrasound

Clinical Signs 60% diagnosed on necropsy Symptoms can be non-specific and episodic Malignant hypertension (>95%) - HALLMARK Sustained hypertension with severe episodes (50%) Normotensive between episodes (25%) Stable hypertension (25%) Normotension does not rule out pheochromocytoma Systolic BP can be >300mmHg Tachyarrhythmia Panting, nervousness Exercise intolerance, weakness (62%), collapse (29%)

Clinical Signs Bleeding diathesis Abdominal mass (10%) Hyphema, retinal detachment Bleeding from the gums CNS bleed Abdominal mass (10%) Palpable mass Abdominal discomfort Abdominal effusion, caudal peripheral edema Can present as an acute retroperitoneal or abdominal bleed Or ascites (pure or modified transudate) due to portal hypertension

Clinical Signs Tumor thrombus – Caudal vena cava Fever PU-PD (29%) Ascites Caudal peripheral edema Fever PU-PD (29%) Anorexia, weight loss Vomiting, diarrhea, constipation

Labwork CBC Serology Urinalysis Anemic if significant bleed Increased white count – response to tumor Serology Liver enzymes usually elevated Can mimic hyperadrenocorticism Urinalysis Poorly concentrated urine with proteinuria

Cardiac Work-Up ECG Echocardiogram – hypertrophic cardiomyopathy Sinus tachycardia early on Catecholamine induced cardiomyopathy leads to life threatening arrhythmias APCs, VPCs, idioventricular rhythms, 3rd degree AV block Echocardiogram – hypertrophic cardiomyopathy Chest x-rays Look for metastasis (3 views) – 15% nodules 3-5mm+ VetBLUE® ultrasound – nodules 1-3mm+

Abdominal Imaging Abdominal mass may be seen on radiographs or on ultrasound Cranial to the kidney(s) Check caudal vena cava for invasion 80% sensitivity, 90% specificity CT 92% sensitivity, 90-100% specificity Adrenal(s) may be enlarged with mixed echogenic pattern effacement of normal architecture (60-80%) Normal ultrasound does not rule out pheochromoctyoma

Abdominal Imaging adrenal tumor invading cava Abdominal mass may be seen on radiographs or on ultrasound Cranial to the kidney(s) Check caudal vena cava for invasion Adrenal(s) may be enlarged with mixed echogenic pattern effacement of normal architecture (60-80%) Normal ultrasound does not rule out pheochromoctyoma

Abdominal Imaging adrenal tumor Abdominal mass may be seen on radiographs or on ultrasound Cranial to the kidney(s) Check caudal vena cava for invasion Adrenal(s) may be enlarged with mixed echogenic pattern effacement of normal architecture (60-80%) Normal ultrasound does not rule out pheochromoctyoma

Cytology FNA of adrenal masses is not recommended Any adrenal tumor has propensity to bleed Catecholamine storm is possible with pheo Cytology is not highly correlated with malignancy with neuroendocrine tumors Cytology can identify the tumor as neuroendocrine Naked uniform round nuclei Cells in rosettes and rows Fine chromatin & inconsistent nucleoli

Cytology FNA of adrenal masses is not recommended Amy adrenal tumor has propensity to bleed Catecholamine storm is possible with pheo Cytology is not highly correlated with malignancy with neuroendocrine tumors Cytology can identify the tumor as neuroendocrine Naked uniform round nuclei Cells in rosettes and rows Fine chromatin & inconsistent nucleoli

Cytology FNA of adrenal masses is not recommended Amy adrenal tumor has propensity to bleed Catecholamine storm is possible with pheo Cytology is not highly correlated with malignancy with neuroendocrine tumors Cytology can identify the tumor as neuroendocrine Naked uniform round nuclei Cells in rosettes and rows Fine chromatin & inconsistent nucleoli

Plasma Free Metanephrines Can measure plasma free metanephrines or fractionated urine metanephrines Much higher in people and dogs with pheochromoctyomas Requires special handling of the sample – contact the lab Add acid, refrigerate, protect from light Phenoxybenzamine, corticosteroids and tricyclic antidepressants can falsely increase metanephrines

Treatment Adrenalectomy is treatment of choice perioperative mortality 50% Pre-treat with phenoxybenzamine for 20 days Reduces perioperative mortality to 20% Treat hypertension If they survive surgery mean survival is 1 year

Acknowledgements Shelly Olin, ACVIM, Alejandro Garcia, Linda Shell, ACVIM (Neurology). Veterinary Information Network (VIN) – Canine Associate.