Diagnosis of gastric submucosal tumors and estimation of malignant risk of GIST by endoscopic ultrasound. Comparison between B mode and contrast- harmonic mode (with videos)

Background: standard B-mode EUS assessment and EUS-guided tissue acquisition present sub-optimal diagnostic yield in the differential diagnosis of gastric submucosal tumors (SMTs). Aims: to evaluate the performances of contrast-enhanced harmonic endoscopic ultrasonography (CH-EUS) to differentiate gastric SMTs and predict malignancy risk of gastrointestinal stromal tumors (GIST). Methods: a retrospective analysis was performed retrieving consecutive patients with gastric SMTs who underwent EUS between 2009 and 2014. Patients with available EUS video recordings and histological diagnosis were included. De-identified videos were presented to experts who made a diagnosis on B-mode EUS and CH-EUS. Results: fifty-four patients (29 female, 64-year-old) were included. Final diagnoses were 40 GISTs (8 high-grade), 9 leiomyomas, 5 rare SMTs. The sensitivity, specificity, and accuracy of B-mode and CH-EUS for the differential diagnosis of GIST were 95.0% vs. 85.0%, 57.1% for both techniques, and 85.2% vs. 77.8%, respectively. The sensitivity, specificity, and accuracy of B-mode and CH-EUS for the estimation of the malignancy GISTs risk were 62.5% vs. 100%, 83.3% vs. 82.1%, and 78.9% vs. 86.1%, respectively. Conclusions: CH-EUS showed better diagnostic performance than B-mode EUS in differentiating leiomyomas and risk stratification of GIST. When considering high-grade GISTs, the addition of CH-EUS allowed an improvement in diagnostic accuracy.