SUN-496 Two for One: A Rare Case of Composite Pheochromocytoma and Ganglioneuroma

Abstract Disclosure: A. Lee: None. S. Stefan: None. R. Berkenblit: None. B. Wong: None. Background: Pheochromocytomas are chromaffin cell tumors that arise in the adrenal medulla or paraganglia and are characterized by excessive catecholamine secretion. A rare subset of pheochromocytomas are composite pheochromocytomas which are composed of pheochromocytoma and other components, most frequently neurogenic tumor.1 We present a case of composite pheochromocytoma with ganglioneuroma. Case Presentation: A 45-year-old woman with hypertension presented with worsening abdominal pain and back pain. On review of systems, she also endorsed headaches and palpitations. The patient was normotensive on amlodipine with a normal heart rate. There is a history of a left sided 1.2 cm adrenal incidentaloma on abdominal CT ten years prior to presentation. A follow-up abdominal CT on current presentation revealed a circumscribed, heterogenous mass in the left adrenal gland measuring 4.4 x 3.0 cm with high attenuation values of 45 HU in the non-contrast phase. These findings raised concern for adrenocortical carcinoma, metastases to the adrenal gland or pheochromocytoma. On biochemical evaluation, she had elevated plasma metanephrines of 162 pg/mL (<=57 pg/mL), plasma normetanephrines of 522 pg/mL (<= 148 pg/mL), 24-hour urine metanephrines of 761 mcg (58-203 mcg), and 24-hour urine normetanephrines of 895 mcg (88-649 mcg). She was started on doxazosin 2mg twice daily and metoprolol 25mg daily in preparation for surgery. The patient then underwent an uncomplicated unilateral laparoscopic adrenalectomy. Pathology from left adrenal resection showed composite pheochromocytoma with ganglioneuroma. Conclusion: Composite pheochromocytomas constitute less than 3% of adrenal gland tumors with the ganglioneuroma subtype being the most prevalent neurogenic component2. Pheochromocytomas and composite pheochromocytomas are clinically, biochemically, and radiographically similar. The diagnosis is typically confirmed through histopathological examination after surgical resection of the tumor. Similar to pheochromocytomas, the treatment of choice for composite pheochromocytomas is pre-operative alpha blockade followed by surgery. Prognosis is generally favorable with complete surgical removal, although long-term follow-up is necessary due to the potential for recurrence or metastasis. Composite pheochromocytomas remain rare and further studies are needed to better understand the significance of this histopathology finding. Presentation: Sunday, July 13, 2025