Endoscopic ultrasonography (EUS) is good in diagnosing submucosal structure of the gastrointestinal tract. We previously reported the “malignant sign (MS)” of EUS findings, combination of the internal echo pattern and the tumor size, for the differentiation of malignant SMTs from retrospective analysis. In this study, we analysed EUS finding of newly diagnosed SMT patients prospectively to compare with the histological findings. EUS was performed in 20 patients with SMTs, and MS was judged. MS was assigned to 1) tumor larger than 20mm with intermediate or mixed irregular echo pattern, or 2) tumor larger than 40mm with hypoechoic pattern. Eleven patients had MS. Eight of the 11 MS SMTs were malignant in histological diagnosis (7 leiomyosarcomas and 1 leiomyoblastoma), and three were benign (leiomyoma, neurinoma and abberent pancreas). Sensitivity of MS in the prospective diagnosis was 100% and the specificity was 75%. MS in EUS derived from the combination of internal echo pattern and tumor size was highly sensitive and specific in this prospective study as in retrospective study. We conclude that MS was clinically useful in differentiation of malignant SMTs from benign SMTs.
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