SUN-282 - From Incidentaloma to Metastatic Disease: The Unpredictable Course of Malignant Pheochromocytoma

Introduction:
Pheochromocytomas are rare adrenal tumors arising from chromaffin cells of the adrenal glands. While most are benign and potentially curable with surgical resection, up to 25% will eventually develop metastatic disease. Approximately 40% are associated with hereditary syndromes, including MEN 2, von Hippel-Lindau syndrome, although sporadic cases remain common. We present a case of adrenal incidentaloma with delayed metastatic progression.

Case:
A 71-year-old male with history of hypertension was referred for evaluation of an incidentally discovered right adrenal mass. He denied palpitations, tremors or headaches. Biochemical evaluation revealed markedly elevated plasma free normetanephrine 2218 pg/ml, total free metanephrine 2244 pg/ml, plasma renin activity elevated at 8.96 ng/ml/h with suppressed aldosterone level of 4 ng/dl. Twenty-four-hour urine studies revealed elevated norepinephrine 220 mcg/24hr, total catecholamines 229 mcg/24hr, normetanephrine 4561 mcg/24 hr and total metanephrines 4657 mcg/24hr. CT abdomen revealed a 5.5 cm right adrenal mass. The patient was initiated on preoperative alpha-adrenergic blockade and subsequently underwent right adrenalectomy. Post-operative evaluation at 12 weeks showed normalisation of plasma catecholamines and metanephrines and the patient remained clinically stable for 5 years. He later presented with new -onset dizziness, dull headaches and gait instability. Extensive neurological evaluation was unremarkable. However, plasma and urine metanephrines were elevated and functional PET imaging was suggestive of metastatic pheochromocytoma. He was treated with chemotherapy and radiation therapy, followed by transition to immunotherapy with ongoing surveillance.

Discussion:
Malignant pheochromocytomas are extremely rare tumors that may manifest years after the initial diagnosis with a reported median age to metastasis of 5.5 years, underscoring the importance of lifelong surveillance in all patients with pheochromocytoma.
The classic triad of palpitations, headache and diaphoresis occurs in only about 12% of patients, emphasizes the role of screening in patients with adrenal incidentalomas. Metastatic pheochromocytoma carries a 5-year survival rate of approximately 60%, with highly variable outcomes. Surgical resection remains the cornerstone of therapy for localized tumors, while systemic chemotherapy and targeted therapies are for metastatic disease based on functional imaging characteristics, tumor burden and rate of progression.

Conclusion:
This case underscores the diagnostic challenges of pheochromocytoma andthe potential for delayed metastatic progression, reinforcing the need for lifelong surveillance. Early recognition of metastatic disease enables timely initiation of systemic therapy and improving outcomes.

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