AJR 2004; 183:1084
© American Roentgen Ray Society
Extratesticular Epidermal Cyst of the Scrotum
Wei Tse Yang1,
Gary J. Whitman1 and
Gary M. K. Tse2
1 Division of Diagnostic Imaging, M. D. Anderson Cancer Center, 1515 Holcombe
Blvd., Box 57, Houston, TX 77030.
2 Department of Anatomical and Cellular Pathology, Prince of Wales Hospital,
30-32 Ngan Shing St., Shatin, Hong Kong, SAR China.
Received October 16, 2003;
accepted after revision May 10, 2004.
Address correspondence to W. T. Yang
(wyang{at}di.mdacc.tmc.edu).
A50-year-old man presented with a painless midline scrotal mass. Clinical
examination revealed a firm, freely mobile extratesticular mass. Both testes
were normal. Gray-scale sonography showed a solid oval extratesticular
hypoechoic mass that exhibited multiple bright internal echoes (Figs.
1A and
1B). Surgical excision was
performed. At histopathologic examination, an epidermal cyst that was lined by
a stratified squamous epithelium with a visible granular layer and filled with
keratinous debris was noted (Fig.
1C). The final histopathologic diagnosis was extratesticular
epidermal cyst.
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Fig. 1A. —50-year-old man with midline intrascrotal extratesticular
epidermal inclusion cyst. Coronal oblique extended-field-of-view sonogram
shows oval solid hypoechoic mass (arrows) separate from testes
(T).
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Fig. 1B. —50-year-old man with midline intrascrotal extratesticular
epidermal inclusion cyst. Longitudinal gray-scale sonogram shows solid oval
hypoechoic mass with multiple bright echogenic reflectors
(arrowheads).
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Fig. 1C. —50-year-old man with midline intrascrotal extratesticular
epidermal inclusion cyst. Photomicrograph of histopathologic specimen shows
epidermal cyst wall with thin layer of benign stratified squamous epithelium
(small solid arrows) and keratinous debris present in cyst (open
arrows). Scrotal skin with basal pigmentation (large solid
arrows) is also noted. (H and E, x100)
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Epidermal inclusion cysts may result from traumatic implantation of
epidermal tissue into the dermis or the subcutis. The implanted tissue may
become cystic and filled with laminated keratin, cholesterol crystals, and
debris. These cysts usually remain asymptomatic unless they become infected,
grow large enough to interfere with normal function, or rupture into the
adjacent soft tissues. If the cyst wall ruptures, a secondary foreign
body-type granulomatous reaction or an abscess may develop
[1].
Extratesticular epidermal cysts have been reported anywhere along the
midline of the median raphe, from the distal penis to the anus. Epidermal
inclusion cysts are believed to represent abnormal embryologic closure of the
median raphe and the urethral groove. Malignant transformation, usually into
low-grade squamous cell carcinoma, is rare.
Langer et al. [2] and Lee et
al. [3] noted that on
sonography, epidermal inclusion cysts commonly appear as hypoechoic lesions
with scattered echogenic reflectors. Lee et al.
[3] stressed that the
sonographic appearances may vary according to the cyst contents, ranging from
an anechoic lesion to a hyperechoic, solid-appearing mass and noted that
ruptured epidermal cysts were more likely to have lobulated contours and show
color Doppler signals, thus mimicking solid masses. Intratesticular epidermal
cysts have been described as having an onionskin appearance on sonography and
MRI, corresponding to multiple layers of keratinous debris. Intratesticular
epidermal cysts may display a bull's eye or target appearance resulting from
dense debris in the center, with internal hyperechoic foci representing
intraluminal calcifications [1,
2]. No color Doppler signals
have been reported in intratesticular epidermal cysts. The similarity of the
sonographic findings in intra- and extratesticular epidermal cysts may be
related to their identical histology. On MRI, an epidermal inclusion cyst
appears as a small, well-defined subcutaneous or cutaneous mass and keratinous
debris may be identified in the mass. These cysts show low signal on
T1-weighted images and high signal on T2-weighted images.
Most extratesticular scrotal epidermal inclusion cysts appear as hypoechoic
masses containing variable echogenic foci and displaying posterior enhancement
but no internal color Doppler signals. The differential diagnosis of
extratesticular scrotal epidermal inclusion cysts includes dermoid cysts,
lipomas, and complex cysts in the tunica and the epididymis. Because the
internal echogenicity of epidermal inclusion cysts varies with their
composition, epidermal inclusion cysts may mimic other solid masses, including
malignant tumors. The suggested treatment for epidermal inclusion cysts is
surgical excision.
References
- Cho JH, Chang JC, Park BH, Lee JG, Son CH. Sonographic and MR
imaging findings of testicular epidermoid cysts. AJR2002; 178:743
-748[Abstract/Free Full Text]
- Langer JE, Ramchandani P, Siegelman ES, Banner MP. Epidermoid cysts
of the testicle: sonographic and MR imaging features.
AJR 1999;173:1295
-1299[Abstract/Free Full Text]
- Lee HS, Joo KB, Song HT, et al. Relationship between sonographic
and pathologic findings in epidermal inclusion cysts. J Clin
Ultrasound 2001; 29:374
-383[Medline]
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