Endoscopic Ultrasound-Guided Fine Needle Biopsy for the Diagnosis of Paraganglioma

Abstract

Paragangliomas are rare neuroendocrine tumors that originate from the extra-adrenal autonomic ganglia. They should be included in the differential diagnosis of retroperitoneal tumors. Endoscopic ultrasound-guided fine needle biopsy (EUS-FNB) has been increasingly used as an effective tool for obtaining diagnostic tissue for histology and molecular studies. We are reporting a patient who was found to have a retroperitoneal mass as an incidental finding and was successfully diagnosed as a non-functional paraganglioma using EUS-FNB without any complications. 50-years-old man who presented to the emergency department after a high-speed motorcycle accident; Computed tomography showed large retroperitoneal mass measuring 9.6 x 12.5 cm. It was a peripherally enhancing, centrally necrotic mass that abuts the Inferior vena cava and aorta. EUS-FNB showed an epitheliod lesion composed of medium sized cells with moderate eosinophilic to clear cytoplasm. Immunostains showed the tumor cells to be positive for CD56 and synaptophysin but negative for pancytokeratins AE1/3 and CAM5.2, Pax-8, CK7, inhibin, S-100 and CD117. This indicates neuroendocrine differentiation, consistent with paraganglioma. He tolerated the procedure well without any complications. Biochemical studies were consistent with non-functioning extra adrenal paraganglioma. The following month, he underwent successful surgical resection of the mass. Paragangliomas can be found in different sites, with the majority being found in the abdomen. They could be either functioning or non-functioning. The functional ones secrete norepinephrine and normetanephrine and represent 36% to 60% of the lesions. Less than 10% could turn malignant. EUS-FNB allows preoperative diagnosis of such lesions. In patients with clinical signs of pheochromocytoma, it is advisable to do 24-hour urine collection of catecholamines and metanephrines before performing EUS-FNB as it is contraindicated in functioning paragangliomas as needle insertion could trigger an adrenergic crisis. In conclusion, EUS-FNB is a safe technique for evaluation of retroperitoneal masses. Physicians should consider biochemical testing to exclude functioning paraganglioma in patients with retroperitoneal masses who have clinical signs of pheochromocytoma prior to performing EUS-FNB to avoid intra-procedural complications.Figure: Abdominal CT (upper left) shows large retroperitoneal peripherally enhancing centrally necrotic mass that measures 9.6 x 12.5 X 10.7 cm. EUS (upper right) shows the mass with the needle going through for fine needle aspiration. FNA cytology slide (bottom left) stained with H&E stain shows small epithelioid cells with moderate pleomorphism, and fine salt and pepper chromatin similar to that seen in neuroendocrine tumors. The paraganglioma mass (bottom right) is shown after surgical resection.