PMON88 A Rare Case of Composite Paraganglioma in the Bladder

BACKGROUND: Paragangliomas are neuroendocrine tumors that arise from embryonic neural crest cells; they are essentially extra-adrenal pheochromocytomas most frequently found in the head and neck. Composite tumors are rare and consist of the presence of two histologically distinct tissues within a single tumor. Additionally rare is the presence of a composite paraganglioma in the retroperitoneum and urinary bladder, of which there are few reported cases. CASE REPORT: We present a case of a 57 year old female who was found to have an incidental pelvic mass noted to progressively increase in size over the years on subsequent imaging. The patient had a cystoscopy and retrograde pyelogram that were both unremarkable. MRI Pelvis showed a 1.8×1.8×1.9 cm rounded, well-circumscribed lesion at the left posterior lateral bladder extending exophytically from the serosa at the ureterovesicular junction. As she had associated hypertension, palpitations, and anxiety, the patient was evaluated for pheochromocytoma.Laboratory workup showed elevated plasma levels of free Metanephrines at 130 (<57 pg/mL), free Normetanephrines at 247 (<148 pg/mL), and a free Total level at 377 (<205 pg/mL). 24-hour urine collection was consistent with mild elevation of Metanephrines at 330 (90-315 mcg/24 h), normal levels of Normetanephrines at 469 (122-676 mcg/24 h), and normal levels of Total urine Metanephrines of 799 (224-832 mcg/24 h). 24-hour urine free Catecholamines showed: Epinephrine of 6 (2-24 mcg/24 h), Norepinephrine of 77 (15-100 mcg/24 h), and a Total (Epi+NE) of 83 (26-121 mcg/24 h), with Dopamine of 220 (52-480 mcg/24 h).Due to mildly elevated metanephrine levels, the patient was started on the alpha-blocker doxazosin. She ultimately underwent a laparoscopic removal of the bladder mass, with pathology reports confirming presence of a composite paraganglioma with atypical features. Additionally, further immunohistochemistry was negative for the SDHB gene mutation in the tissue samples obtained. CONCLUSION: Composite paragangliomas of the urinary bladder are very rare. Certain genetic pathologic variants carry an increased risk for malignancy and possible metastasis; therefore, these neuroendocrine tumors usually require targeted mutation testing. At this time, the pathogenesis of composite paragangliomas is still largely unknown, with little information available about treatment options and clinical outcomes. Presentation: Monday, June 13, 2022 12:30 p.m. - 2:30 p.m.