Imaging studies play a vital role in the diagnosis and management of testicular cancer. Ultrasound is primarily used for initial diagnosis, and CT is the standard for cancer staging. MRI provides an equally powerful diagnostic alternative to CT for use in certain circumstances. The use of PET is limited in tumor characterization, but, with the advent of new tracers, PET is gaining acceptance for the evaluation of treatment response as well as recurrence.
Sonographic imaging of the testes represents the reference standard imaging evaluation, with sensitivity of near 100% when combined with physical examination (Fig. 1).
Ultrasound can distinguish intra- and extra-testicular lesions and is undertaken in most cases before orchiectomy . Testicular tumors are typically well defined and hypoechoic compared with normal testicular tissue but can be heterogeneous with calcification or cystic changes . Increased vascularity of a lesion is not specific to testicular tumors.
In cases in which the diagnosis is in question, additional information can be gained with MRI. Solid testicular tumors have lower signal intensity on T2-weighted MRI in contrast with the high signal intensity of normal testicular parenchyma. One study evaluated MRI of the testes before orchiectomy in 33 patients with T1- and T2-weighted images using a 1.5-T MRI unit.
The sensitivity and specificity of MRI in differentiating benign from malignant intratesticular lesions were 100% and 87.5%, respectively.
Furthermore, the accuracy of MRI for assigning pathologically confirmed T category was 92.8% . The role of MRI of the testis in place of ultrasound remains to be clearly determined. However, it offers reliable and detailed information in the case of equivocal ultrasound findings or in the absence of a skilled sonographer. On occasion, the initial presentation may be a retroperitoneal mass, with testicular imaging not revealing an evident lesion. In these cases, a testicular malignancy must be considered because the primary testicular tumor may have “burned out” and no longer be evident or it may appear more subtle on imaging [12, 13] (Fig. 2). A more unusual presentation would be that of an extragonadal GCT. Extragonadal GCTs are essentially of the same histology as testicular malignancies but develop outside of the testis, commonly in the pineal gland, mediastinum, retroperitoneum, or sacrum [14, 15]. In either of these situations, tumor markers or biopsy may provide insight to the diagnosis.
The finding of testicular microlithiasis (Fig. 3) is commonly present on ultrasound imaging in patients with testicular malignancy. Historically, the contribution of testicular microlithiasis to the risk of malignancy has been controversial; however, more recent data have shown that the presence of microlithiasis on an otherwise normal testicular ultrasound does not predispose the patient to testicular malignancy . One study of sonographic screening in 1504 healthy United States Army Reserve recruits revealed an incidence of testicular microlithiasis of 5%, or 1000 times greater than the incidence of testicular malignancy . It appears the presence or absence of testicular microlithiasis is not significantly associated with risk for malignancy, and there is no good evidence to support a role for imaging surveillance in the absence of additional risk factors [18, 19].