Leiomyoma of the epididymis: Ultrasound and MRI findings

Clinical History

66-year-old man, with a slightly painful mass in left hemiscrotum. Scrotal ultrasound showed a rounded, slightly hypoechoic 2x2 cm mass with wohrl-shape pattern and narrow bands of shadowing. MRI showed isointense signal in T1 and hypointense signal in T2, with mild enhancement after contrast administration. Pathological examination revealed leiomyoma.

Imaging Findings

A 66-year-old man presented with a firm, slightly painful mass in the left hemiscrotum. He reported no history of trauma or infection to the scrotum. All laboratory tests and tumor markers were normal. High resolution US revealed a 2x2- cm, well defined extratesticular mass located inferior to the testis and completely seperable from it. The lesion had a hypoechoic appearance with wohrl-shape pattern and multiple small posterior narrow shadowings without evidence of calcifications. No infiltration of surrounding strucutres. Mild bilateral hydroceles and grade II left-sided varicocele were also noted. Color Doppler US (CDUS) showed mild central vascularity within the mass. and sagittal T2 axial T1 pre and post contrast MRI was performed using a 1.5 T MRI machine (Siemens Medical solutions, Erlangen, Germany), in the form of: Sagittal T1 pre and post contrast MRI confirmed the ultrasound findings with the mass appeared isointense in T1, and hypointense in T2 with mild enhancement after contrast administration. The lesion was classified as likely benign.

Discussion

US is very useful tool in diagnosing scrotal masses. It can distinguish intratesticular from extratesticular masses, which is advantageous compared with physical examination, since most of the extratesticular masses are benign, while most of the intratesticular masses are malignant [1]. Solid epididymal masses have generally non specific criteria and should undergo list of differential diagnosis [2]. Of the most common solid paratesticular neoplasms that should be considered: Adenomatoid tumor: The most common tumour of the epididymis, accounting for nearly one third of all paratesticular neoplasms. Affects mainly men 20 years or more, with usual unilateral involvement. [3] US shows usually oval isoechoic mass, however it may appear predominantely cystic in some patients. [3] MRI demonstrates well defined solid mass seperable from the testis, exhibiting isointense signal to the testis in T1 and hyperintense signal relative to the normal epididymis in T2. [4] Lipoma: The most common benign neoplasm of the paratesticular tissues. US shows homogenous hyperechoic signal mass. MRI and CT provide confirmation with the tumor having hypodense attenuation at CT and hyperintense signal at T1 MRI. [3] Fibrous pseudotumour: Reactive fibrous proliferation of paratesticular tissue, with history of trauma or inflammation in 30% of cases. US shows complex mass of mixed echogenicity, which appears lobulated with multiple frond like projections arising from the tunica vaginalis in MRI. [3] Leiomyoma: The second most common neoplasm of the epididymis (6% of cases). It usually manifests in the fifth decade of life as a slowly growing, non tender scrotal mass. [3] They are usually unilateral, but bilateral tumors were also reported. [4] US reports described a solid hypoechoic or heterogeneous mass, with sometimes multiple areas of calcifications. [5,6] In 1996, Hertzberg et al [7] reported an important US feature of leiomyoma, multiple narrow areas of shadowing not cast by calcifications. Such pattern was also noticed in uterine myomas; so that, they suggested that it could be an important sign in diagnosing epididymal leiomyoma. In 2004 Chee-Wai et al [1] confirmed this sign in a case of leiomyoma arising from the tunica albuginea. We also detected this sign; therefore we can support its importance in diagnosing epididymal leiomyoma. Chee-Wai et al [1] reported another important sign, which is wohrl-shape appearance, and attributed this sign to the histopathological structure of leiomyoma, as being a tumour composed of wohrling bundles of smooth muscle cells. They attributed the depiction of this sign to the use of high frequency transducer together with the superficial location of the lesion. We also detected this sign, and we agree with them in both of its importance and cause of detection. To the best of our knowledge, this is the first case that reported the MRI and US findings of an epididymal leiomyoma. In T2-weighted image, the lesion shows diffuse hypointense signal similar to uterine myoma which could be attributed to the histopathologic composition of leiomyoma.

Differential Diagnosis List

Final Diagnosis

Epidymal leiomyoma as confirmed by pathological and histochemical studies.

URL:	https://www.eurorad.org/case/6351
DOI:	10.1594/EURORAD/CASE.6351
ISSN:	1563-4086