Is Endoscopic Ultrasonography Adequate for the Diagnosis of Gastric Schwannomas?

Gastrointestinal subepithelial lesions (SELs) are masses or bulges covered by normal appearing mucosa and are usually found incidentally during endoscopy. There are various types of gastric SELs, ranging from benign lesions to lesions with malignant potential. Endoscopic ultrasonography (EUS) is the most reliable diagnostic modality for gastric SELs, and provides helpful information for differential diagnosis as well as guidance in clinical decision-making. EUS allows evaluation of the sonographic nature of SELs, including the size, layer of origin, border, echogenicity, and the presence of cystic or echogenic foci. Typical EUS features may lead to specific diagnosis in cases of a cyst or lipoma. However, the accuracy of EUS alone is limited in the diagnosis of gastric SELs, especially in differentiating hypoechoic lesions, and preoperative differential diagnosis is often difficult. The mesenchymal tumors originating from the fourth sonographic layer (muscularis propria) include leiomyoma, gastrointestinal stromal tumors (GISTs), and schwannomas. The differentiation of these tumors is crucial because GISTs have malignant potential, whereas most leiomyomas and schwannomas follow benign clinical courses. The diagnosis of GISTs is supported by immunohistochemical staining for CD117, the protein product of the c-kit proto-oncogene. However, the acquisition of tissue for histopathologic diagnosis is not always satisfactory. In line with this, there have been reports regarding characteristics of GISTs and sonographic features predictive of malignant potential such as size, irregular margins, internal cystic spaces, presence of echogenic foci, and presence of lymphadenopathy. In contrast, only a few studies have evaluated the endosonographic characteristics of gastric schwannomas. In this issue of Clinical Endoscopy, Yoon et al. evaluated EUS findings of 27 gastric schwannomas that were confirmed pathologically after surgical resection. Most cases were asymptomatic and usually discovered incidentally during screening endoscopy. They analyzed 14 EUS features including the location, echogenicity, homogeneity, sonographic layer of origin, growth pattern, the presence of marginal haloes, internal echogenic spots, and lobulated margins. The most frequent location of the tumors was the middle third of the stomach (63.0%). Characteristic EUS features of gastric schwannomas were heterogeneously hypoechoic lesions with distinct borders and marginal haloes. Notably, the authors compared the echogenicity of the tumors to that of the surrounding normal proper muscle layer, and 17 lesions (63.0%) exhibited decreased echogenicity. Calcification (3.7%), cystic change (7.4%), and surface ulceration (11.1%) were relatively uncommon findings. Histopathologically, all tumors were S100 positive and 96.3% showed cuff-like lymphoid infiltration at the peReceived: September 7, 2016 Accepted: November 8, 2016 Correspondence: Kee Don Choi Department of Gastroenterology, Asan Digestive Disease Research Institute, Asan Medical Center, University of Ulsan College of Medicine, 88 Olympic-ro 43beon-gil, Songpa-gu, Seoul 05505, Korea Tel: +82-2-3010-5813, Fax: +82-2-476-0824, E-mail: keedon@amc.seoul. kr