SUN-505 “Biochemical Storm In Silence: An Incidentally Discovered Pheochromocytoma With Life-threatening Potential”

Abstract Disclosure: A. Farid: None. D. Carrizo: None. Introduction: Pheochromocytomas are rare catecholamine-secreting tumors of the adrenal medulla that may remain clinically silent despite excessive hormonal activity. Although classic symptoms include paroxysmal hypertension, palpitations, diaphoresis, and headaches, many cases—especially those incidentally discovered—present without overt signs. However, unrecognized tumors can precipitate life-threatening complications such as hypertensive crises, arrhythmias, myocardial infarction, or stroke due to excessive circulating catecholamines¹. Clinical Case: A 53-year-old male with no history of hypertension, cardiac disease, or adrenergic symptoms underwent low-dose chest CT for lung cancer screening, which incidentally revealed a right adrenal mass. Dedicated adrenal protocol CT identified a 2.6 x 3.8 x 4.6 cm heterogeneously enhancing lesion with 58.9% absolute washout—indeterminate but concerning given size and imaging features.Endocrine workup showed normal aldosterone and cortisol. However, biochemical evaluation revealed markedly elevated plasma normetanephrine (916 pg/mL), total metanephrines (983 pg/mL), norepinephrine (2277 pg/mL), and dopamine (115 pg/mL), despite the patient being entirely asymptomatic. 24-hour urine collection further confirmed biochemical activity with normetanephrines 1724 mcg/24h (ref: 122-676), total metanephrines 1859 mcg/24h (ref: 224-832), and metanephrine 135 mcg/24h (ref: 90-315), over a urine volume of 2815 mL confirming the diagnosis of a biochemically active pheochromocytoma.The patient was pre-treated with titrated alpha-blockade using doxazosin, followed by beta-blockade, and underwent successful laparoscopic adrenalectomy. Pathology confirmed pheochromocytoma with focal capsular invasion but no malignant features. Postoperatively, catecholamines normalized and antihypertensives were discontinued. Conclusion: This case highlights the deceptive nature of biochemically active yet asymptomatic pheochromocytomas. Left undetected, such tumors pose a silent but serious risk for sudden cardiovascular events. Routine biochemical screening of adrenal incidentalomas remains crucial. Lifelong follow-up is warranted due to potential recurrence and genetic implications². References: 1. Lenders JWM, Duh QY, Eisenhofer G, et al. Pheochromocytoma and Paraganglioma: An Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab. 2014;99(6):1915-1942. 2. Bausch B, Wellner U, Bausch D, et al. Long-term prognosis of patients with pheochromocytoma: focus on clinical follow-up, risk of recurrence, and management of genetic predisposition. J Clin Endocrinol Metab. 2014;99(1):35-43. Presentation: Sunday, July 13, 2025