6998 Giant Pheochromocytoma: A Retrospective Single-Center Study

Abstract Disclosure: B. Bahrani Fard: None. N. Nikravangolsefid: None. J. Maroun: None. A. Cross: None. T. Foster: None. T. McKenzie: None. W. Young Jr: None. B.M. Dy: None. M. Lyden: None. I. Bancos: None. Background: Giant pheochromocytomas (PHEO), defined based on size > 10 cm, are rare. Data on clinical presentation, management, and prognosis of giant PHEOs are scarce. Objectives: to determine prevalence of giant PHEO and compare presentation, management, and outcomes of patients with giant vs non-giant PHEOs. Methods: We conducted a single-center retrospective cohort study of consecutive patients with giant PHEO and randomly chosen patients with non-giant PHEO (referents) at 6:1 ratio, evaluated between 2000-2023. All variables were extracted from the electronic medical record. Results: Of 828 patients with PHEO evaluated between 2000 and 2023, 31 (3.7%) had giant PHEO (median size 12 cm, IQR 10.0-13.5). In comparison to referents (n=186, median size 4 cm, IQR, 2.9-5.0), patients with giant PHEO were similar in age (median age 53 vs 55 years, P=.55), more frequently discovered based on symptoms (52% vs 32%, P=.04), and less likely to be bilateral (3% vs 12%, P=.31). Genetic testing was performed in 103 (48%) of patients, without group differences, however, patients with giant PHEO were less likely to have an associated germline mutation detected (7% vs 47%, P=.004). Patients with giant PHEO had more symptoms of catecholamine excess (median of 2 vs 1, P=.04) and presented with a higher prevalence of severe metanephrine excess >10 times above upper normal range (76% vs 30%, P