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Circularity Is a Potential Noninvasive Diagnostic Indicator to Differentiate Gastric Submucosal Tumors

Background and Aims: Noninvasive, imaging diagnosis of gastrointestinal mesenchymal tumors (GIMTs) is still difficult. This study aimed to develop a novel diagnostic method of GIMTs via endoscopic ultrasonography (EUS) using circularity. Methods: In a derivation series, we retrospectively collected 50 GIMTs 2–5 cm in diameter of two institutions. After selecting one EUS still image showing the maximal area per lesion, two endoscopists who were blind to the histological diagnosis assessed circularity, a surrogate indicator of roundness (range, 0–1; 1 = a true circle), with an image-analyzing software. Median circularity of three types of GIMT was compared, and the cutoff value to differentiate a group from other groups was presented by drawing a receiver operating characteristic curve. Subsequently, we assessed the diagnostic ability of circularity in 91 GIMTs which were retrospectively collected from the other two institutions by using the optimal cutoff value presented in the derivation series. Results: The circularity in leiomyomas indicated 0.70 and was significantly lower than that of gastrointestinal stromal tumors (0.89), schwannomas (0.90), and their combined group. When leiomyomas were diagnosed as the circularity of <0.8305, which was presented as the optimal cutoff value, the diagnostic accuracy, sensitivity, and specificity in the validation series were 73.6%, 80.0%, and 72.4%, respectively. Conclusion: The data demonstrated that leiomyomas significantly exhibited more distortion than other GIMTs. That implies that the difference in shape, which is objectively determined as circularity, is useful to noninvasively discriminate leiomyomas from other GIMTs.