SUN-908 Mediastinal Paraganglioma: A Rare Presentation of a Rare Tumor

BACKGROUND Paragangliomas (PPGL’s) are extra-adrenal chromaffin-cell originating tumors that arise from the para-aortic ganglia and are exceptionally rare making up only 1% of the mediastinal tumors. They are slowly growing and highly vascular tumors associated with high morbidity and mortality due to proximity and invasion into the heart, great vessels. The majority of them are asymptomatic and hence discovered incidentally. Surgical resection remains the standard of care with good long term survival. We describe a case of a young male with middle mediastinal PPGL who remained asymptomatic despite large functional tumor. CLINICAL CASE A 38-year old Arab male with no previous smoking history was referred to our hospital for evaluation of mediastinal mass that was incidentally noted on an echocardiogram done 1 year ago in his home country when he presented with intermittent exertional shortness of breath for 10 years. The workup done there with CT chest revealed a large mediastinal mass measuring 10.4×8.8×8.6 cm extending into ascending aorta, right pulmonary artery, right superior pulmonary vein, right and left atria as well as the main bronchi bilaterally invading the superior vena cava. However, he had no further treatment until he was seen 1 year later in the US at another institution where biochemical testing showed elevated plasma norepinephrine of 2697 (70-750 pg/ml, supine), dopamine 7667 (<30 pg/ml). 24hr-urine studies showed elevated normetanephrine of 3418 (111-419 mcg/24hr), metanephrine 3488 (200-614 mcg/24hr), and Homovanillic acid (HVA) 51.5 (<0.8 mg/24hr). He underwent endobronchial ultrasound with mediastinal tissue biopsy of the mass that revealed pheochromocytoma. The patient was subsequently referred for cardiovascular intervention at our hospital and endocrinology was consulted for pre-operative preparation. One week before surgery, he was started on doxazosin 2mg daily followed 3 days later by propranolol 10 mg twice daily and recommend high salt and fluid intake. The patient underwent surgical resection of the mass and pathology showed mediastinal PPGL. The postoperative course was complicated by bradycardia with the placement of a permanent pacemaker. He recovered well after surgery with the resolution of symptoms and a significant decline in catecholamines to urine normetanephrine of 385 mcg/24hr and metanephrine 497 mcg/24hrs. There was no evidence of metastatic or residual disease on follow-up CT chest 5 months later. CONCLUSION There are limited case reports of PPGL in the middle mediastinum. This case highlights that mediastinal PPGL’s can remain clinically silent for many years prior to the presentation which can lead to delayed diagnosis, yet a strong collaborative team approach between oncology, cardiovascular surgery and endocrinology can confer favorable clinical outcome.