Adenomatoid tumour of epididymis: ultrasonographic evaluation with surgical correlation

Clinical History

A 16-year-old boy presented with a palpable mass in the right hemiscrotum. The mass had been detected 2 months before but during the past week it became mildly painful. Clinical examination confirmed the presence of a palpable, hazelnut-like mass. His medical history was unremarkable.

Imaging Findings

The patient was referred for scrotal ultrasound. This examination revealed the presence of a rounded solid and homogeneously iso- to hyperechoic mass measuring 13x8.9 mm located on the lower pole of the right testis and adjacent to the tail of epididymis. There was a small cystic area inside the mass. Colour Doppler and power Doppler techniques identified only limited blood flow signals within the mass. On the other hand, the epididymis and juxtapositioned vas deferens showed normal vascularity. (Fig. 1) The boy underwent elective surgery where this roughish mass was found near the lower pole of the testis, adherent to the tail of epididymis. (Fig. 2) It was excised from the tail of the epididymis with adequate margins and sent for histopathological examination. (Fig. 2) There were no complications, the patient had a normal postoperative course and was discharged the next day.

Discussion

Adenomatoid tumours (AT) constitute a group of rare unilateral benign solid extratesticular masses which have a mesothelial origin and can arise from the epididymis, the tunica vaginalis or spermatic cord, representing one third of all paratesticular tumours. [1-3] They are the most common tumours of the epididymis after lipoma, usually affecting its tail. When it comes to radiology practice, they are second to cysts. The majority of these tumours present as asymptomatic palpable scrotal masses in patients aged 20-50 years. [1, 4] Pain is reported in 30% of these patients. [5] AT can also be found in female reproductive organs. [2] Laboratory examinations including α-fetoprotein and β-human chorionic gonadotropin are unremarkable. [2]
AT are extratesticular lesions that grow in a noninvasive pattern. When situated next to the testis, they may be considered to be intratesticular. Ultrasound is the primary imaging modality to characterize and accurately locate intrascrotal masses, excluding the presence of cysts. [1, 2] AT appear as solid, well-circumscribed extratesticular rounded or oval-shaped masses of variable echogenicity. [1, 4] Their size ranges from 0.4 to 5 cm. [5] In most cases, AT appear isoechoic and less frequently hypoechoic or with mixed echogenicity. [2] An either hyperechoic or hypoechoic rim may be evident in benign epididymal tumours like AT. [6] Hydrocele may coexist with the tumour in 20% of cases. In only a minority of patients, AT may be demonstrated as predominantly cystic using ultrasound. [5] Colour Doppler technique should be always used to assess the vascularity of scrotal masses. It has been shown that the degree of blood flow inside a focal lesion is significantly higher in patients with epididymitis than in those with benign masses. [6] The main question in point is to exclude malignancy preoperatively. MRI can be used in that respect to further evaluate AT, which are identified as masses with low signal intensity on T2-weighted images and variable enhancement after gadolinium administration. [1]
Surgery is the treatment of choice with local excision of the tumour thanks to its benign nature. Malignant forms of AT have been described but are extremely rare. [2] There are no reported patients with metastases or recurrence after surgery. [3] Histologic examination of AT reveals flattened or cuboidal epitheliod cells lined in tubules within a stroma of loose collagen. [5] Infarction of these tumours caused by a trauma is an infrequent complication. [7]
In conclusion, the diagnosis of AT should be always kept in mind once an extratesticular solid mass is accurately identified as epipidymal on ultrasound. [2]

Differential Diagnosis List

Final Diagnosis

Adenomatoid tumour of epididymis

URL:	https://www.eurorad.org/case/12854
DOI:	10.1594/EURORAD/CASE.12854
ISSN:	1563-4086