Efficacy of endoscopic ultrasound-guided fine-needle aspiration for schwannoma: six cases of a retrospective study

Abstract

Schwannomas are difficult to diagnose using imaging alone. Endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA) is an effective and safe tissue sampling technique. Nevertheless, few reports have described EUS-FNA for schwannoma. This study evaluates the efficacy of EUS-FNA for diagnosing schwannoma. This retrospective study examined six consecutive schwannoma patients who were diagnosed as having schwannoma either from EUS-FNA results or from surgically resected specimens. The primary endpoint was diagnostic accuracy of EUS-FNA for schwannoma. The secondary endpoint was EUS-FNA safety. Based on cytomorphologic features and immunocytochemistry results after EUS-FNA, 4 out of 6 patients (66.7%) were diagnosed with schwannoma. The diagnoses before EUS-FNA were the following: 3 cases of gastric subepithelial lesion (SEL, suspicious for gastrointestinal stromal tumor), 1 case of intraperitoneal tumor, 1 case of retroperitoneal tumor, and 1 case of pancreatic tumor, with sizes of 15-44 mm (median 36 mm). No case was diagnosed as schwannoma solely based on image findings. Two cases of gastric SELs could not be diagnosed as schwannoma by EUS-FNA before surgery. Inadequate sampling and a lack of additional material for immunohistochemical studies could have engendered less-definite diagnoses in those cases. No procedural adverse events occurred. The diagnostic accuracy rate of EUS-FNA for schwannoma is somewhat low. However, tissue samples were obtained safely using this method. Moreover, it is an important procedure for diagnosing schwannoma, which cannot be diagnosed solely from image findings.