Tubular ectasia of the rete testis: a benign testicular entity diagnosed on imaging

Clinical History

Dilatation or tubular ectasia of the rete testis (TERT) is a well-known benign intratesticular entity, for which the clinical, as well as the imaging findings may unable a correct diagnosis and the avoidance of invasive tests, as unnecessary biopsy or orchiectomy.

Imaging Findings

A 58-year old man was referred to the Urology department with a six-month history of painless swelling of the right hemiscrotum. On physical examination a firm mass was palpable in the head of the right epididymis and a normal ipsilateral testis was separated from the extratesticular mass. Sonographic examination of the scrotum revealed the presence of a large right cystic mass involving the area of the head of the epididymis. An ovoid cluster of small anechoic structures within the mediastinum of the right testis, measuring was also detected (Fig. 1a). Doppler sonography showed absence of blood flow within the intratesticular lesion (Fig. 1b). Scrotal MR imaging examination was performed using fast spin-echo T2-weighted images and spin-echo unenhanced and contrast-enhanced T1-weighted images. A large right spermatocele, a moderate hydrocele and a multilocular intratesticular lesion, were detected (Fig. 2). A smaller lesion involving the apex of the left testis was also revealed, the same lesion not detected on sonography. The intratesticular masses were located in the region of the mediastinum and had signal intensity similar to that of water. Their signal intensity was identical to that of the spermatocele on all pulse sequences. After the administration of gadopentetate dimeglumine (Fig. 2d), none of the above lesions enhanced. Based on the clinical and imaging findings, suggestive for the diagnosis of tubular ectasia of the rete testis, spermatocelectomy was performed. Follow-up sonogram, two years after the initial presentation, revealed no change of the imaging findings.

Discussion

The majority of intratesticular masses are malignant; therefore orchiectomy is mandatory to rule out malignancy [1]. However, differentiating benign from malignant intratesticular lesions is critical, since the correct preoperative characterization may obviate an unwarranted biopsy or surgery [1, 2]. Dilatation or tubular ectasia of the rete testis (TERT) is a well-known benign intratesticular entity [1, 2-6]. The incidence of TERT is unknown, although is reported in up to 4.3% of the routine scrotal sonographic examinations [3]. The etiology is believed to be obstructive, since the majority of patients with TERT have a history of possible obstruction of the spermatic ducts, such as chronic epididymitis, spermatoceles, as in this case, trauma, scrotal or inguinal interventions [3-11]. The sonographic findings of this entity are typical and allow a confident diagnosis in the majority of cases [3-8]. A group of small anechoic tubular structures, involving the area of the mediastinum, with so solid components and no mass effect, devoid of blood flow, as in our case, represent the typical findings of TERT. Tartar et al [9] first described the characteristic MR appearance of TERT in six patients, reporting signal homogeneity, similar to that of the coexisting spermatoceles, hypointensity on T1 and proton density-weighted images and no lesion discrimination from the normal testicular parenchyma on spin-echo T2-weighted images. In this case, we used fast-spin echo T2-weighted images, and the signal intensity was higher than that of the normal testicles on these sequences. Our case was typical of a bilateral TERT, demonstrating signal intensity similar to that of the coexistent spermatocele on all pulse sequences and no enhancement after contrast material administration [3, 9-11]. MR imaging examination of the scrotum is best recommended in cases in which the sonographic findings are equivocal or nondiagnostic, to avoid unnecessary surgical explorations. TERT is easily differentiated from testicular tumors due to its unique localization in the region of the mediastinum testis, its characteristic imaging features, both on sonography and MR examination, the absence of palpable intratesticular mass, the frequent coexistence of spermatoceles ant its occurrence in greater age, when compared with testicular malignancies [3, 4]. However, dilatation of the rete testis due to a tumor occlusion has also been described [3] and should always be evaluated in the differential diagnosis. The papillary adenocarcinoma of the rete testis may manifest as a multilocular cystic lesion [12], but in this case the mass is usually palpable and is associated with the presence of solid elements on imaging evaluation.Differential diagnosis should also include the intratesticular varicocele and the cystic dysplasia of the testis. Intratesticular varicocele is an extremely rare condition, easily diagnosed by the presence of blood flow during rest or the Valsalva maneuver [13]. The cystic dysplasia of the testis is another rare, nonneoplastic entity, which may have similar sonographic and histologic appearance with TERT [14]. However, this entity is mainly diagnosed in children and often associated with renal or excretory duct malformations [15].

Differential Diagnosis List

Final Diagnosis

Tubular ectasia of the rete testis

URL:	https://eurorad.org/case/5385
DOI:	10.1594/EURORAD/CASE.5385
ISSN:	1563-4086