MON-391 A Rare Case of Giant Composite Pheochromocytoma with Unusual Clinical Presentation

Introduction With increasing access to imaging, more Pheochromocytomas are being diagnosed in the workup of adrenal incidentalomas. We present a rare case of a giant composite pheochromocytoma with unusual clinical presentation and discuss the importance of suspecting such lesions even in the absence of classical clinical presentation. Case Presentation A 37-year-old female had an accidental finding of a right adrenal incidentaloma measuring 5 cm in size in 2015. The patient was asymptomatic. Her outpatient workup revealed 4 and 10-fold elevation of urinary and plasma metanephrines respectively, highly suspicious for pheochromocytoma. The patient was lost to follow up. She presented two years later with severe right-sided flank pain and headache. Repeat MRI abdomen revealed 9 cm right adrenal mass with central necrosis and interval enlargement compared to MRI in 2015. Clinically patient had a non-functioning adrenal mass with borderline low blood pressure and normal Heart rate. Repeat hormonal levels confirmed Pheochromocytoma. Dexamethasone suppression test was normal which ruled out Cushing’s syndrome. Clonidine suppression test consistent with Pheochromocytoma. She underwent right robotic adrenalectomy after adequate alpha blockage and volume repletion. She had uneventful postoperative periods and no immediate complications. Histopathology of the specimen revealed a composite pheochromocytoma with ganglioneuroma component. Discussion Pheochromocytoma can be incidentally discovered as an adrenal mass. The incidence of normotension in Pheochromocytoma is 5-15%. Even if clinically silent, mass should be carefully screened for the possibility of functional activity. Patients with composite tumor can present as normotensive or hypotensive. A possible hypothesis is that ganglioneuroma component of the mass may modify the hormonal symptoms of Pheochromocytoma by metabolizing the catecholamine. It is speculated that a larger proportion of ganglioneuroma component will produce a greater regulation effect. Pheochromocytoma-ganglioneuroma composites are clinically and radiologically indistinguishable from Pheochromocytomas and need to be managed similarly. Such cases need to be treated even if clinically silent because of the risk of life-threatening hypertensive crisis in future Conclusion Hormone screening evaluation is necessary for all adrenal incidentalomas. All clinically diagnosed pheochromocytomas should be surgically excised to prevent lethal outcomes.