Ultrasound features for pediatric testicular lesions: 20 years of ultrasound practice interpreted through the 2022 WHO Classification

Background: Testicular lesions are rare in pediatric populations. The World Health Organization standardized the classification of testicular tumors for urological and male genital tumors in 2022. Ultrasound is highly sensitive in detecting testicular lesions in children; however, the ultrasound features that distinguish malignant from benign lesions remain unclear. We aimed to identify ultrasound features that differentiate benign and malignant testicular lesions in pediatric patients. In addition, we evaluated the role of ultrasound in pediatric testicular tumors based on the new guidelines.

Methods: We retrospectively reviewed the clinical data and ultrasound images of 84 testicular lesions in 79 pediatric patients aged 0–18 years (≤216 months), who underwent testicular sonography between April 2004 and October 2023 at West China Hospital. Prepuberty was defined as 0–12 years of age. Univariate and multivariate logistic regression analyses were conducted to compare ultrasound features between benign and malignant tumors across all 84 lesions, 66 primary tumors, and 65 prepubertal lesions. Continuous variables were compared between groups using the Mann-Whitney U test, and Fisher’s exact test was used for categorical variables.

Results: Univariate analysis showed that among the 84 total lesions, the malignant group exhibited a more diffuse lesion range compared with the benign group (P<0.001). Among 84 total lesions or 66 primary tumor lesions, the malignant group exhibited more hypoechoic and isoechoic echoes, unclear margins, absence of calcification, and increased vascularity (P<0.001). Furthermore, in 66 primary tumor lesions, the malignant group also exhibited non-complex echo and the small hypoechoic nodule structures (P<0.001). There were no significant differences in microlithiasis among all groups (all P>0.05). In the multivariate analysis, among the total lesions group or primary tumor group, hypoechoic and isoechoic patterns, as well as absence of calcification, remained important features of malignant manifestations (all P<0.001). Margin circumscription was statistically significant only in the total lesions group (P=0.001), whereas lesion size was statistically significant only in the primary tumor group (P=0.006). In 65 prepubertal lesions, malignant lesions presented more hypoechoic and isoechoic echoes (P<0.01), and clear margins (P=0.034) were associated with a reduced risk of malignancy. Among 84 total lesions, the predictive power of echo pattern was the highest [area under the curve (AUC) =0.815], followed by calcification (AUC =0.795) and lesion size (AUC =0.712). The predictive power of echo patterns and calcification remained good in 66 primary tumors (AUC =0.818 and 0.838, respectively) and 65 prepubertal lesions (AUC =0.842 and 0.820, respectively).

Conclusions: The echo pattern shows the highest predictive value in total lesions and prepubertal lesions, while calcification is more important for primary tumors. Different imaging features may be required to optimize the prediction of benign and malignant testicular lesions.