Differential Diagnosis of Nonpalpable Testicular Lesions: Qualitative and Quantitative Contrast-enhanced US of Benign and Malignant Testicular Tumors

Purpose: To evaluate the diagnostic accuracy of unenhanced and quantitative contrast-enhanced ultrasonography (US) in the differential diagnosis of small nonpalpable testicular lesions. Materials and Methods: The local review board approved the protocol, and all patients provided written informed consent. One hundred fifteen patients (median age, 34 years; age range, 14-61 years) with nonpalpable testicular lesions were consecutively enrolled between 2006 and 2012 and underwent unenhanced scrotal US, contrast-enhanced US, surgical enucleation, and at least 18 months of follow-up. Clinical and histologic features were recorded, and qualitative and quantitative analysis of contrast-enhanced US time-intensity curves were performed. Logistic regression analysis was performed to explore features of malignancy. Receiver operating characteristic (ROC) curves were developed for cumulative unenhanced and contrast-enhanced US scores. Results: All lesions were 1.5 cm or smaller. Forty-four of the 115 patients (38%) had malignant tumors, 42 had benign tumors (37%), and 29 (25%) had nonneoplastic lesions. The features at unenhanced US that enabled the best differentiation of tumors versus nonneoplastic lesions and benign versus malignant tumors were parenchymal microlithiasis (26 of 86 patients with tumors vs five of 29 patients with nonneoplastic lesions [P = .178]; four of 42 patients with benign lesions vs 22 of 44 patients with malignant tumors [P < .001]), irregular margins (26 of 86 patients with tumors vs three of 29 patients with nonneoplastic lesions [P < .001]; eight of 42 patients with benign lesions vs 18 of 44 patients with malignant tumors [P < .001]), and internal vascularization (70 of 86 patients with tumors vs seven of 29 patients with nonneoplastic lesions [P < .001]; 28 of 42 patients with benign lesions vs 42 of 44 patients with malignant tumors [P < .001]). For contrast-enhanced US, the rapidity of wash-in (34 of 44 patients vs 15 of 42 patients, P < .001) and washout (33 of 44 patients vs five of 42 patients, P < .001) were the parameters that best differentiated malignant from benign tumors, with a typical prolonged washout observed in Leydig cell tumors (12 of 21 patients, P < .001 when compared with seminomas). Overall, the combination of unenhanced and contrast-enhanced US achieved a high accuracy in the diagnosis of small testicular malignancies (area under the ROC curve performance: 0.927; 95% confidence interval: 0.872, 0.981). Conclusion: Benign testicular tumors are frequent incidental findings. Quantitative scrotal contrast-enhanced US is a noninvasive diagnostic tool that could improve the differential diagnosis and individualized management of small testicular lesions. (C) RSNA, 2014