8683 Composite Pheochromocytoma/Paraganglioma-Ganglioneuroma: Biochemical And Radiological Features

Abstract Disclosure: S. Agarwal: None. A.P. Dackiw: None. F. Nwariaku: None. J.E. Mosquera: None. L. Jia: None. M.G. Roden: None. O. Hamidi: Advisory Board Member; Self; Corcept Therapeutics. Introduction: Composite pheochromocytoma/paraganglioma with ganglioneuroma (PHEO-GN or PGL-GN) is a rare tumor consisting of chromaffin cells or ganglia tissue combined with a developmentally related neurogenic tumor. Composite tumors can be present in up to 10% of PHEO and are rare with just over 100 cases reported in published literature. We present a case series of patients with PHEO-GN and PGL-GN seen at our tertiary care center to examine their natural history, clinical, radiological, and biochemical characteristics. Methods: We conducted a retrospective longitudinal follow-up study of consecutive adult patients with histologically-proven PHEO-GN and PGL-GN seen between 2013 and 2023. We collected and summarized data on demographics, laboratory findings, radiological results, and clinical outcomes. Results: The cohort comprised 10 patients (60% women): 8 with PHEO-GN (1 diagnosed on autopsy), 1 with PGL-GN, and 1 with PHEO-ganglioneuroblastoma. The median age at diagnosis was 47 years (interquartile range [IQR], 35-60). Most (80%) tumors were discovered incidentally. The prevalence of a genetic syndrome was 40% and included multiple endocrine neoplasia (MEN) 2A, MEN 4, Neurofibromatosis 1, and hereditary PHEO-PGL syndrome due to succinate dehydrogenase type B gene mutation. Nine patients (90%) had biochemically functional tumors with adrenergic biochemical phenotype in 89% and noradrenergic in 11%. The tumor associated with MEN 4 also had dopamine secretion. The median elevation above the upper normal limit of plasma metanephrine was 7.4 (IQR, 1.6-12), 24-hour urine metanephrine was 7.12 (IQR, 3.7-8.8), plasma normetanephrine was 1.7 (IQR, 1.5-1.9), and 24-hour urine normetanephrine was 2.9 (IQR, 2.4-3.5). The median tumor size at the time of diagnosis was 4.2 cm (IQR, 3.3-5.2). The median pre-contrast HU on CT imaging was 37 HU (IQR, 20-40). The median time to surgical excision from the diagnosis was 2.7 months (IQR, 1.9-4.6). All patients that underwent surgery were alive without recurrence of disease at last follow-up visit with a median follow-up of 14.5 months (IQR, 0.5-18.4). Conclusions We present a series of 10 consecutive patients with composite PHEO-GN and PGL-GN. The prevalence of genetic syndrome (40%) was much higher than previously reported (up to 25% in prior reports). PHEO or PGL component of these tumors is commonly biochemically functional with metanephrine and normetanephrine elevation commonly seen. Metastatic or recurrent disease was not observed in our cohort, suggesting favorable outcomes after surgical resection. Presentation: 6/2/2024