Abstract
<title>Abstract</title> <p>Objective Investigating the diagnostic accuracy of contrast-enhanced ultrasound(CEUS) in differentiating benign, borderline, and malignant adnexal masses classified as inconclusive under the International Ovarian Tumour Analysis (IOTA) simple rules. Methods Retrospective analysis of 81 IOTA-indeterminate adnexal masses evaluated with CEUS (April 2019–December 2025). With postoperative histopathological diagnosis as the gold standard, all cases were classified into benign (n = 40), borderline (n = 20), and malignant (n = 21) groups. Univariate differential analysis and multivariate logistic regression analysis were applied to identify imaging features associated with pathological classification. A logistic prediction model was established, and its diagnostic performance was assessed by receiver operating characteristic (ROC) curve analysis. Internal validation was conducted using 1000-iteration bootstrap resampling to assess model stability. Results Univariable analysis identified significant intergroup differences in five CEUS features (all P < 0.05): microcystic pattern (MCP), capsular integrity, enhancement homogeneity, peak enhancement intensity, and maximum enhanced component diameter. Multivariable ordinal logistic regression confirmed MCP absence (OR = 0.453, 95% CI 0.225–0.912, P = 0.026), intact capsule (OR = 0.030, 95% CI 0.004–0.238, P < 0.001), and hypoenhancement (OR = 0.301, 95% CI 0.135–0.669, P = 0.003) as independent predictors of pathological classification. The three-category prediction model incorporating these features achieved AUCs of 0.920 (100% sensitivity, 65.9% specificity) for benign lesions, 0.673 (90.0% sensitivity, 65.6% specificity) for borderline tumors, and 0.904 (66.7% sensitivity, 98.3% specificity) for malignant lesions. Bootstrap internal validation confirmed good model stability. Conclusions In adnexal masses with indeterminate risk assessment using the IOTA simple rules, the post-contrast MCP, capsular continuity, and peak enhancement intensity represented three crucial imaging indicators for distinguishing benign, borderline, and malignant lesions. The preliminary prediction model established in this study may serve as a useful reference for differentiating benign, borderline, and malignant adnexal masses that cannot be classified definitively using the IOTA simple rules.</p>