Contrast-Enhanced Harmonic Endoscopic Ultrasonography for Diagnosing Gastric Subepithelial Tumors.

Background/Objectives: Contrast-enhanced harmonic endoscopic ultrasonography (CH-EUS) is a promising tool for differentiating gastric subepithelial tumors (SETs). However, most published studies have mainly included gastrointestinal stromal tumors (GIST) and leiomyomas in the gastrointestinal tract, not limited to gastric SETs. This study evaluated the diagnostic performance of CH-EUS in gastric SETs encountered in clinical practice. Methods: We retrospectively analyzed 68 patients who underwent CH-EUS for gastric SETs between March 2021 and July 2025 at our institution. Gastric SETs were classified into benign (n = 27: ectopic pancreas, leiomyoma, schwannoma, glomus tumor, plexiform fibromyxoma, desmoid tumor, solitary fibrous tumor, and abscess) and GIST groups (n = 41). CH-EUS features, including arterial enhancement, irregular vessels, and diffuse enhancement, were assessed. Histopathological confirmation was obtained through EUS-guided fine-needle biopsy or endoscopic/surgical resection. Results: The GIST group showed significantly higher rates of arterial enhancement (95.1% vs. 74.1%, p = 0.024), irregular vessels (51.2% vs. 22.2%, p = 0.017), and diffuse enhancement (87.8% vs. 66.7%, p = 0.035) than the benign SETs. The diagnostic performance of arterial enhancement showed a sensitivity of 95.1% and specificity of 25.9%, while irregular vessels demonstrated a sensitivity of 51.2% and specificity of 77.8%, and diffuse enhancement showed a sensitivity of 87.8% and specificity of 33.3%. When combining ≥2 CH-EUS features, the sensitivity and specificity were 92.7% and 33.3%, respectively, with an overall accuracy of 69.1%. The presence of all three features yielded a specificity of 81.5% but a lower sensitivity (46.3%). Conclusions: CH-EUS exhibited a high sensitivity but low specificity in differentiating GISTs from various benign gastric SETs when using a combination of at least two CE-EUS features, including arterial enhancement, irregular vessels, and diffuse enhancement.