Retroperitoneal schwannoma diagnosed by endoscopic ultrasound-guided fine-needle aspiration.

A 59-year-old white man was referred for evaluation of epigastric pain that was radiating to his back and a 5-kg weight loss over 6 months. A computed tomography (CT) scan revealed a heterogeneous low-attenuation tumor, measuring 5cm in size, adjacent to the celiac artery and the pancreatic body (●" Fig.1). Sectorial endoscopic ultrasound (GF-UCT140-AL5; Olympus America Inc., New York, USA), coupled to an ultrasound unit (Prosound alfa-5 SX; Aloka), detected a retroperitoneal well-circumscribed, hypoechoic mass, which measured 5×4cm and was located immediately above the celiac tripod (●" Fig.2). Endoscopic ultrasound-guided fineneedle aspiration (EUS-FNA) was performed by three passes of a 22-gaugeneedle (EchoTip Ultra Echo-22; Cook Medical, WinstonSalem, North Carolina, USA). Histology revealed a spindle cell tumor that was strongly immunoreactive for S-100, thereby defining it as a schwannoma (●" Fig.3). The tumor was successfully removed despite its adherence to the celiac tripod arteries (●" Fig.4). A schwannoma is a tumor arising from neural crest-derived Schwann cells in the sheaths of peripheral nerves. Retroperitoneal schwannomas are very rare, comprising less than 6% of all retroperitoneal tumors [1]. They are clinically asymptomatic until the tumors reach a large size and cause compressive symptoms. Diagnosis is difficult because of their rarity, asymptomatic course, and the lack of any specific diagnostic blood test or features on imaging studies [2]. Tumor size is related to its malignant potential and to the formation of cysts [3]. Surgery is the treatment of choice and is usually curative [4]. The findings on EUS generally reveal a well-circumscribed hypoechoic mass. EUS-FNA of retroperitoneal tumors is a valuable method for the preoperative diagnosis of schwannomas [2].