B-mode high-frequency (greater than or equal to 10 MHz) grayscale scrotal sonography performed with a linear-array transducer is the initial imaging modality used to evaluate testicular masses suspicious for malignancy. GCTs are often intratesticular masses, and US can accurately distinguish between intratesticular and extratesticular lesions [3]. SGCTs appear hyperechoic and homogenous compared with healthy testicular tissues. They may be lobulated or multinodular and rarely have calcifications (30%) or cystic spaces (10%) [4]. NSGTs often appear as multicomponent masses on grayscale sonography and can be solid or solid-cystic lesions [5•]. Color-coded duplex sonography can be used to analyze the vascularization of intratesticular masses with malignant lesions often demonstrating increased vascularity compared with background testis tissue [4]. Grayscale US (combined with clinical presentation) can be used to distinguish between GCTs and benign testicular masses such as testicular hematoma, epidermoid cyst, adrenal rests, splenogonadal fusion, and sex-cord stromal tumors (Table 1).

Shear wave elastography (SWE) is an US modality that provides quantitative color-coded maps of tissues stiffness that are displayed in real time with B-mode images through a detection pulse that measures the speed of shear waves through the tissue of interest [6].

Pedersen et al. compared testicular stiffness in normal testicular tissue (n = 130), testicular microlithiasis (n = 99), and GCTs (n = 19) using SWE. Their analysis revealed significantly higher mean velocity on SWE in the testicular cancer group compared to those with normal testicular tissue and testicular microlithiasis (p < 0.001) [7]. Rocher et al. evaluated the performance of combined B-mode, color doppler, and SWE US in distinguishing between benign and malignant testicular lesions. Their evaluation included 89 focal testicular masses with patients categorized by pathology: malignant tumors (SGCTs, NSGCTs, malignant sex cord Sertoli cell tumor (n = 1), and myeloma (n = 1)), burned-out tumors, and benign lesions. The following five parameters using SWE were recorded for each testicular lesion: average stiffness with standard deviation (SD), max stiffness, average stiffness/normal testicular tissue stiffness ratio, and max stiffness/normal testicular tissue stiffness ratio. The most relevant conventional US and SWE parameters that best discriminated malignant tumors and burned-out tumors from benign lesions were peripheral vascularization, grouped microliths, and max stiffness/normal testicular tissue stiffness ratio with 92% sensitivity, 96% specificity, 94% accuracy (p < 10−4), and area under the receiver operating characteristic curve (AUROC) ± 95% confidence interval (CI) of 0.98 ± 0.20. Without the SWE parameters, conventional US had 55% sensitivity, 97% specificity, 74% accuracy (p < 10−4), and AUROC ± 95% CI of 0.88 ± 0.11. Their group concluded that SWE combined with color doppler US and B-mode US can significantly improve characterization of testicular masses, however, their study was limited by use of a single US operator and subjectivity of the conventional US parameters [7, 8•].

Another method of ultrasonography with potential to help distinguish between benign and testicular GCTs is contrast-enhanced US (CEUS). A bolus of contrast material (microbubbles) is introduced intravenously during simultaneous US of the testicle to demonstrate tissue perfusion. Isidori et al. performed unenhanced and CEUS on 115 patients with non-palpable testicular lesions who subsequently underwent surgical resection. The rapidity of wash-in and washout were the CEUS parameters that best differentiated malignant and benign tumors. Combination of unenhanced and CEUS was highly accurate in diagnosing testicular malignancies (AUROC 0.927 with 95% CI [0.827, 0.981]) [9]. CEUS has yet to be widely validated in the USA and is not routinely used in testicular US.