Teaching Case

A 24-year-old man presents a two-week history of increased volume and palpation of a mass in the left testicle.

The primary suspicion was the presence of a testicular tumour, prompting the initiation of the investigation with an ultrasound (US)  using a high-frequency transducer. In this US, a well-defined paratesticular mass was identified as dependent on the tunica albuginea. This mass appeared hypoechoic with heterogeneous characteristics, measuring 34 x 15 x 17 mm, and exhibited hypervascularity on colour Doppler US (CDUS). Additionally, there were at least 10 adjacent nodules that also depended on the tunica albuginea of the testicle, displaying vascularity. The left testicle was of normal morphology and echogenicity.

It was suspected to be a malignant lesion like a mesothelioma or a sarcomatous lesion due to his location and hypervascularity, so the patient was referred directly for a radical orchiectomy. The final biopsy confirmed the presence of a tumour derived from the tunica albuginea composed of spindle-shaped mesenchymal cells, consistent with an adenomatoid tumour.

Adenomatoid tumours are benign tumours of mesothelial origin, accounting for approximately 30% of paratesticular tumours. They are mostly located in the epididymis, but a smaller number may be found in the tunica albuginea and less frequently in other structures, such as the spermatic cords [1–3]. These tumours tend to occur in men aged 30 to 50 years and often present as palpable, asymptomatic scrotal masses with slow growth and benign nature [4]. On physical examination, they appear as painless, firm lesions with smooth borders, generally measuring 1 to 2 cm, rarely exceeding 5 cm [5].

Ultrasound is the imaging modality of choice for the initial evaluation of testicular and scrotal diseases [6]. An adenomatoid tumour often appears as an oval, homogeneous paratesticular mass, of variable echogenicity, either hypoechoic, isoechoic, or hyperechoic compared to the adjacent testicular parenchyma, with poor vascularity on CDUS. Adenomatoid tumour characteristics in the US are sometimes not specific, making differentiation from other possible lesions like fibrous pseudotumour or malignant neoplasm challenging [7–9]. In those cases, magnetic resonance imaging (MRI) of the scrotum can be complementary, depicting an adenomatoid tumour as hypointense on T2-weighted sequences and exhibiting similar enhancement after gadolinium intravenous administration in comparison to the testicular parenchyma [9]. MRI can be used to clarify the tumour location and the characteristics of the tissue to differentiate it from a benign or malignant lesion, achieving a better histologic characterisation [10]; even with a diagnosis of a malignant lesion, it can help to assess the aggressivity and the search of distant metastatic lesions.

The presented case is the first in the literature to describe a multifocal adenomatoid tumour from the tunica albuginea with multiple nodules and hypervascularity mimicking other malignant lesions such as mesothelioma.

The resemblance of malignant neoplasms to some adenomatoid tumours makes it challenging to decide between radical or partial orchiectomy. Ultrasound is the primary tool for characterisation, and understanding the various presentations is crucial to avoid unnecessary radical orchiectomies [11].

In conclusion, adenomatoid tumours are benign paratesticular tumours that can manifest in a variety of ways. The presented clinical case is the first in the literature to describe a multifocal adenomatoid tumour in the tunica albuginea. This uniqueness underscores the importance of surveillance and recognition of uncommon variants, as understanding the diversity in the presentation of these tumours could be crucial for clinical planning and decision-making.

All patient data have been completely anonymised throughout the entire manuscript and related files.