Beyond germ cell tumors, unusual testicular and extra-testicular masses and mass-like lesions: MRI and US pictorial review

An Overview of the Role of Multiparametric MRI in the Investigation of Testicular Tumors

Simple Summary

Although conventional ultrasonography remains the primary imaging modality for the assessment of testicular tumors, multiparametric MRI of the scrotum, which combines morphologic and functional data, serves as a powerful adjunct. Based on the recommendations issued by the Scrotal and Penile Imaging Working Group of the European Society of Urogenital Radiology, scrotal MRI is strongly recommended after equivocal US findings. In cases of testicular masses, the main clinical indications are as follows: lesion characterization when sonographic findings are non-diagnostic, discrimination between germ-cell and non-germ-cell testicular tumors, local staging of testicular tumors in patients who are candidates for testis-sparing surgery, and preoperative histological characterization of testicular germ-cell tumors in selected cases. This article aims to provide an overview of the role of multiparametric MRI in the investigation of testicular tumors.

Abstract

Conventional ultrasonography represents the mainstay of testis imaging. In cases in which ultrasonography is inconclusive, scrotal MRI using a multiparametric protocol may be used as a useful problem-solving tool. MRI of the scrotum is primarily recommended for differentiating between benign and malignant testicular masses when sonographic findings are ambiguous. This technique is also accurate in the preoperative local staging of testicular tumors and, therefore, is recommended in patients scheduled for testis-sparing surgery. In addition, MRI may provide valuable information regarding the histological characterization of testicular germ-cell tumors, in selected cases. Scrotal MRI may also help in the differentiation between testicular germ-cell neoplasms and non-germ-cell neoplasms. Axial T1-weighted imaging, axial and coronal T2-weighted imaging, axial diffusion-weighted imaging, and coronal subtracted dynamic contrast-enhanced imaging are the minimum requirements for scrotal MRI. A variety of MRI techniques—including diffusion tensor imaging, magnetization transfer imaging, proton MR spectroscopy, volumetric apparent diffusion coefficient histogram analysis, and MRI-based radiomics—are being investigated for testicular mass characterization, providing valuable supplementary diagnostic information. In the present review, we aim to discuss clinical indications for scrotal MRI in cases of testicular tumors, along with MRI findings of common testicular malignancies.

Testicular Germ Cell Tumours—The Role of Conventional Ultrasound

Testicular tumours are the most common tumours found in young males and germ cell tumours account for 95% of testicular tumours. Ultrasound is the first-line radiological investigation for imaging of the testis. This article outlines how to undertake an ultrasound examination, including optimal patient position, scanning technique and imaging parameters. Classification of germ cell tumours is provided, and salient imaging features of different tumours are described. Difficulties and pitfalls of ultrasound are described, including tumours found after a trauma presentation, orchitis causing diagnostic difficulties and imaging of small testicular lesions. Other uses of ultrasound are outlined, including looking for a primary testicular tumour following the discovery of retroperitoneal lymph nodes, imaging when tumour-makers increase, local recurrence in the scrotum, and for solid organ biopsy in metastatic disease. Conclusion: Ultrasound remains the first-line of investigation for imaging of the testis, and conventional ultrasound still plays a large role in imaging. On ultrasound alone, accurate morphological characterisation of tumours remains a challenge, despite the imaging features that can be seen in different tumour types. Therefore, histology following orchidectomy of a germ cell tumour remains the gold standard for accurate tumour characterisation.

Ewing's sarcoma of the male external genitalia: a case report and review of the literature

BACKGROUND

Ewing's sarcoma (ES) within the genitourinary tract are relatively unheard of and those within the external male genitalia are even rarer. To our knowledge, this is the first known case of primary ES within the paratesticular region in an adult.

CASE PRESENTATION

We present a case of a 24-year-old man with a right sided testicular mass on examination that was initially characterized as an adenomatoid tumor on ultrasound. After the patient was lost to follow up over the course of 9 months, the testicular mass grew significantly and was excised with pathology revealing primary paratesticular Ewing's sarcoma. This rare case emphasizes the importance of elucidating between the broad differentials of paratesticular masses, including the rare presentation of primary ES and adds a review of the literature of ES in the external male genitalia.

CONCLUSIONS

Rare differentials such as this case should be considered in patients with paratesticular masses. Further diagnostic and management algorithms for extraosseous Ewing Sarcoma, particularly in the adult population, are warranted.

When to ask for an MRI of the scrotum

Background

Multiparametric MRI (mpMRI) of the scrotum has been established as a useful second‐line diagnostic tool for the investigation of scrotal diseases. Recently, recommendations on clinical indications for scrotal MRI were issued by the Scrotal and Penile Imaging Working Group of the European Society of Urogenital Radiology.

Objective

To update current research on when to ask for an MRI of the scrotum.

Methods

PubMed database was searched for original articles and reviews published during 2010–2021.

Results

Eighty‐three articles fulfilled the search criteria. Scrotal MRI is mainly recommended after inconclusive US findings or inconsistent with the clinical examination and should be asked in the following cases: differentiation between intratesticular and paratesticular lesions (in rare cases of uncertain US findings), characterization of paratesticular and intratesticular lesions (when US findings are indeterminate), discrimination between germ cell and sex cord‐stromal testicular tumors, local staging of testicular malignancies (in patients planned for testis‐sparing surgery), differentiation between seminomas and non‐seminomatous tumors (when immediate chemotherapy is planned and orchiectomy is delayed), assessment of acute scrotum and scrotal trauma (rarely needed, in cases of non‐diagnostic US findings) and detection and localization of undescended testes (in cases of inconlusive US findings). Although preliminary data show promising results in the evaluation of male infertility, no established role for mpMRI still exists.

Conclusion

Multiparametric MRI of the scrotum, by assessing morphologic and functional data represents a valuable problem‐solving tool, helping to improve our understanding on the nature of scrotal pathology and the process of spermatogenesis. The technique may improve patient care and reduce the number of unnecessary surgical procedures.