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 5 cm 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 × 4 cm and was located immediately
above the celiac tripod ([Fig. 2]).
Fig. 1 A computed tomography (CT) scan showing a heterogeneous low-attenuation tumor measuring
5 cm in size, adjacent to the celiac artery and the pancreatic body, that is displacing
the splenic vessels anteriorly.
Fig. 2 Linear-array endoscopic ultrasound (EUS) showing: a a retroperitoneal hypoechoic heterogeneous mass with well-defined borders measuring
5 × 4 cm; b the absence of a hyperechoic interface between the tumor and the celiac artery, and
no evidence of thrombi or collateral circulation.
Endoscopic ultrasound-guided fine needle aspiration (EUS-FNA) was performed by three
passes of a 22-gauge needle (EchoTip Ultra Echo-22; Cook Medical, Winston-Salem, 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]).
Fig. 3 Histopathological findings of the cell block specimen showing: a large cohesive groups of spindle cells with nuclear palisading on hematoxylin and
eosin (H&E) staining (original magnification × 100); b diffuse nuclear and cytoplasmic on immunostaining with polyclonal S-100 (original
magnification × 50).
Fig. 4 Macroscopic appearance of the cut surface of the resected tumor showing a firm, yellowish,
4.5-cm well-circumscribed, encapsulated solid tumor with focal areas of hemorrhage.
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].
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