CASE 13801 Published on 14.06.2016

Extratesticular epidermal inclusion cyst of the scrotum (ECR 2016 Case of the Day)


Uroradiology & genital male imaging

Case Type

Clinical Cases


A.C. Tsili1, G.V. Mouka1, A.A. Ntorkou1, D. Giannakis2, S. Stavrou2, M.I. Argyropoulou1

(1) Department of Clinical Radiology
(2) Department of Urology,
Medical School, University of Ioannina;

7 years, male

Area of Interest Genital / Reproductive system male ; Imaging Technique MR, MR-Diffusion/Perfusion, Ultrasound, Ultrasound-Colour Doppler
Clinical History
A 7-year-old boy presented with a painless, palpable right scrotal mass. No history of prior trauma or surgery was reported. Clinical examination revealed the presence of an elastic, freely-movable right scrotal mass, separated from the ipsilateral testis. Laboratory analysis, including testicular tumour markers was unremarkable.
Imaging Findings
Sonography of the scrotum reported the presence of an ovoid, well-demarcated heterogeneous right extratesticular mass, with mild posterior sound enhancement (Fig. 1). The lesion was mainly hypoechoic, with scattered echogenic reflectors (Fig. 1a, b) and absence of vascularity on colour Doppler examination (Fig. 1c).
MRI examination of the scrotum followed. The presence of a right extratesticular mass (Fig. 2) was confirmed, in close proximity to the ipsilateral spermatic cord. The lesion had signal intensity similar to that of normal testis on both T1 and T2-weighted images, therefore detected mainly hyperintense on T2-weighted sequences, surrounded by a hypointense halo (Fig. 2a). Restricted diffusion was noted on DW images (Fig. 2c). Dynamic-contrast enhanced MRI after gadolinium administration showed no lesion enhancement (Fig. 2d). The testes, the epididymides and the spermatic cords were normal. The testicular tunicae were intact.
Epidermal inclusion cysts (EICs), the most common type of simple epithelial cyst, are typically well-encapsulated, subepidermal, mobile nodules. They may occur anywhere, but are most often found on the scalp, face, neck, trunk, and back [1–10]. They are formed by the inclusion of keratinising squamous epithelium within the dermis, which becomes cystic, filled with loosely packed lamellae of keratin debris, cholesterol, and water [1-4].
EICs in the scrotum are rare. There, they are more often located within the testis, representing about 1% of intratesticular masses [11,12]. In the case of the extratesticular EIC, an abnormal closure or associated degenerative process of the median raphe and urethral groove is the possible aetiologic factor.
EICs in the scrotum are seen in children and adults. They are usually asymptomatic, detected as firm, freely moveable extratesticular masses. However, they become symptomatic when complicated with infection, rupture into the adjacent soft tissues or when they grow large enough to interfere with normal function. Malignant transformation, usually into low-grade squamous cell carcinoma, is very rare. Complete surgical excision is the treatment of choice [1-10].

Imaging perspective:
Ultrasound represents the primary imaging modality in the evaluation of scrotal lesions [13]. The sonographic appearance of an EIC varies from an anechoic lesion to a hyperechoic, solid mass, depending on its content. They are more often detected as well-demarcated hypoechoic masses, with multiple scattered reflectors from the keratinous debris and posterior sound enhancement, without vascularity on Doppler sonography [1-3]. The sonographic appearance of EICs has been described by Lee et al., suggesting five characteristic patterns in 24 EICs in various locations: type I, with alternating hypoechoic and hyperechoic eccentric rings (onionskin appearance); type II, hypoechoic lesion with hyperechoic centre (target sign); type III, hypoechoic lesion with scattered echogenic reflectors; type IV, inhomogeneous lesion; and type V, with areas of varying echogenicity [3].
MRI is considered an important adjunct imaging modality in the investigation of scrotal pathology [14]. On MRI, EICs are reported as well-demarcated, hyperintense extratesticular masses, surrounded by a low signal capsule on T2-weighted images. T1-weighted sequences often reveal homogenous or heterogeneous low signal intensity. After gadolinium administration, lack of contrast enhancement is observed, a finding strongly suggestive for the diagnosis of benignity [1, 2, 4].
Differential Diagnosis List
Extratesticular epidermal inclusion cyst of the scrotum
Adenomatoid tumour
Epidermal inclusion cyst
Final Diagnosis
Extratesticular epidermal inclusion cyst of the scrotum
Case information
DOI: 10.1594/EURORAD/CASE.13801
ISSN: 1563-4086