SAT-499 A Silent Pheochromocytoma

Abstract Disclosure: O. Onwudiwe: None. A.M. Aviles Melendez: None. R. Zafar: None. Background: Pheochromocytoma is a rare neuroendocrine tumor originating from chromaffin cells in the adrenal glands. Most cases are benign and may be unilateral or bilateral, with an incidence of 0.29 to 0.66 cases per 100,000 person-years. Symptoms include paroxysmal attacks of headaches, sweating, palpitations, and hypertension, although some cases, like the one described here, can be asymptomatic. Case: A 64-year-old woman, a former smoker with no significant history, was referred to the endocrine clinic for an incidental left adrenal mass identified during lung cancer screening. CT and MRI confirmed a 4 cm left adrenal mass. She was asymptomatic, with a family history notable for breast and lung cancer in her sister and prostate cancer in her father. Biochemical evaluation revealed elevated plasma and urine metanephrines and normetanephrines. Dopamine, renin, and aldosterone were negative. Following alpha and beta blockade, she underwent a left adrenalectomy. Pathology confirmed pheochromocytoma, with tumor cells staining positive for synaptophysin, chromogranin, GATA-3, and focal staining for S-100 and SOX-10. SDHB immunohistochemical staining showed retained expression. She recovered well and remained asymptomatic at her one-month follow-up. Discussion: Pheochromocytoma, though rare, can present asymptomatically, as in this case. Risk factors include genetic and non-genetic contributors. A significant proportion is linked to inherited syndromes, such as MEN2A, MEN2B, NF1, and VHL. Germline mutations in RET, VHL, NF1, SDHB, and other genes are also associated with pheochromocytomas and paragangliomas. Even asymptomatic pheochromocytomas require treatment due to the risk of hypertensive crises and severe cardiovascular complications, including myocardial infarction, pulmonary edema, stroke, and Tako-Tsubo cardiomyopathy. Excessive catecholamine secretion can precipitate multi-organ failure or a pheochromocytoma crisis, characterized by hyperthermia, encephalopathy, and labile blood pressure. Without treatment, pheochromocytomas can metastasize, leading to poor prognosis and significantly increased mortality. Historical data show that up to 50% of cases were identified post-mortem due to fatal cardiovascular events. Conclusion: Untreated pheochromocytoma poses risks of fatal cardiovascular events, multi-organ failure, and metastasis, all contributing to increased mortality. Current guidelines strongly advocate for treating all pheochromocytomas, regardless of symptoms, to prevent these potentially life-threatening outcomes. Presentation: Saturday, July 12, 2025