DOI: 10.1148/rg.24si035223
RadioGraphics 2004;24:S243-S246
© RSNA, 2004
Epidermoid Cyst of the Testis: Radiologic-Pathologic Correlation1
Alma G. Loya, MD,
Jonathan W. Said, MD and
Edward G. Grant, MD
1 From the Department of Radiology, University of California at Los Angeles. Received December 10, 2003; revision requested January 14, 2004; final revision received April 12; accepted April 19. All authors have no financial relationships to disclose. Address correspondence to E.G.G., USC University Hospital, 1500 San Pablo St, 2nd Fl Imaging, Los Angeles, CA 90033 (e-mail: edgrant@usc.edu).
Index Terms: Epidermoid, 847.311 • Testis, cysts, 847.311 • Testis, neoplasms • Testis, US, 847.1298
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History
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A 27-year-old man was referred for ultrasonographic (US) evaluation of a painless right testicular mass. The mass had been present for 3 years and had recently increased in size. Physical examination revealed no evidence of lymphadenopathy or gynecomastia. Laboratory test results, including levels of the tumor marker serum ß–human chorionic gonadotropin, were normal. The patient was admitted for surgery. Inguinal orchiectomy was performed, and the postoperative course was uneventful.
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Imaging Findings
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Testicular US revealed a 1.9 x 1.8 x 1.9-cm solid mass within the right testis with concentric rings of hypoechogenicity and hyperechogenicity ("onion ring" appearance). The center of the mass was slightly echogenic. The surrounding parenchyma and the right epididymis were normal (Fig 1). The patient also had a normal chest radiograph.
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Figure 1a. Longitudinal (a) and transverse (b) US images of the right testis show a well-circumscribed intratesticular mass (cursors) in the lower medial aspect of the testis. The mass contains alternating rings of hyperechogenicity and hypoechogenicity and has a slightly echogenic center. The surrounding testis is normal.
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Figure 1b. Longitudinal (a) and transverse (b) US images of the right testis show a well-circumscribed intratesticular mass (cursors) in the lower medial aspect of the testis. The mass contains alternating rings of hyperechogenicity and hypoechogenicity and has a slightly echogenic center. The surrounding testis is normal.
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Pathologic Evaluation
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At gross examination, the specimen consisted of a testis measuring 4.5 x 2.5 x 2 cm with an attached spermatic cord 8 cm in length. Bisection of the testis revealed a hard white lesion with concentric rings of white-yellow pastelike material within the testicular parenchyma. The lesion was well encapsulated and sharply delineated from the surrounding parenchyma (Fig 2).
At microscopy, keratinizing squamous epithelium was seen to surround the keratin-filled cyst. The adjacent testicular parenchyma contained a few atrophic tubules; the remaining parenchyma contained normal tubules. The epididymal ducts and the spermatic cord were normal. There were no elements of mature teratoma present (Fig 3).
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Figure 3a. (a) Low-power photomicrograph (original magnification, x80; hematoxylin-eosin stain) shows normal testis (T) and an epidermoid cyst (C). The cyst wall contains keratinized squamous epithelium (E). The lumen of the cyst contains keratinized debris (arrow). A few atrophic testicular tubules are present (arrowheads). (b) Higher-power photomicrograph (original magnification, x130; hematoxylin-eosin stain) shows hyperkeratotic squamous epithelium (E) lining the cyst.
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Figure 3b. (a) Low-power photomicrograph (original magnification, x80; hematoxylin-eosin stain) shows normal testis (T) and an epidermoid cyst (C). The cyst wall contains keratinized squamous epithelium (E). The lumen of the cyst contains keratinized debris (arrow). A few atrophic testicular tubules are present (arrowheads). (b) Higher-power photomicrograph (original magnification, x130; hematoxylin-eosin stain) shows hyperkeratotic squamous epithelium (E) lining the cyst.
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The alternating rings of white-yellow pastelike material corresponded to the layers of keratinizing squamous epithelium (seen as alternating rings of hyperechogenicity and hypoechogenicity at US). The keratin debris seen at both gross and histologic examination corresponded to the slightly echogenic center seen at US.
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Discussion
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Epidermoid cyst of the testis is a rare but benign lesion that has a controversial histologic origin; therefore, the clinical management of the cyst has been controversial during the past decades (1,2). First described in 1942 by Dockerty and Priestley (3), epidermoid cyst accounts for 1%–2% of all testicular lesions. The majority of patients are in the 2nd to 4th decades of life, although patient age ranges from 3 to 77 years (1,2,4). The reported cases have occurred in white and Asian persons. There is a slightly higher prevalence in the right testis (1,4,5). There has been one case report of bilateral epidermoid cysts, whereas there have been four reported cases of multiple cysts (1,4). Patients with multiple cysts have included one with Gardner syndrome, two with Klinefelter syndrome, and one with a microscopic focus of primary carcinoid tumor in the cyst wall (1,2,4). Multiple cysts are occasionally found in cryptorchid testes (1,2).
The clinical manifestation of epidermoid cysts is indistinguishable from that of the much more common malignant germ cell tumor. Most patients are asymptomatic, with the mass being detected either at self-examination or during physical examination as a smooth, firm, painless mass with a mean diameter of 2–3 cm (1–8). A minority of patients experience scrotal pain, scrotal enlargement, or vague discomfort (1,5). In one report of five patients (7), a palpable mass had been present for 1 month to 5 years.
US has been the mainstay for the preoperative diagnosis of epidermoid cysts and reveals a well-circumscribed, intratesticular lesion with normal surrounding testis. The lesion can contain a hypoechogenic concentric ring surrounding an echogenic center, with or without a hyperechogenic rim ("bull’s-eye" or "target" appearance), or it can contain alternating hypoechogenic and hyperechogenic concentric rings (onion ring appearance) (Fig 1) (7,8).
In some studies, investigators incorporated the use of magnetic resonance (MR) imaging. In one study (9), the mass was shown to have a peripheral rim with low signal intensity on both T1- and T2-weighted images and a circumferential zone of higher signal intensity surrounding a low-signal-intensity central zone. In the other study (7), investigators described alternating concentric rings of low and high signal intensity on T1- and T2-weighted images. The central echogenic center seen at US corresponds to the lower-signal-intensity zone seen at MR imaging and is thought to represent the keratin debris. Likewise, the hypoechogenicity or alternating echogenicity seen at US corresponds to the surrounding higher signal intensity seen at MR imaging and represents the lipid- and water-containing material of the cyst. The squamous cell–lined capsule creates a hyperechogenic rim at US and a low-signal-intensity rim at MR imaging. No contrast material enhancement has been demonstrated at MR imaging, nor has the lesion been shown to be vascular at US.
The differential diagnosis of intratesticular masses is limited, and the unique onion ring appearance first described by Malvica (8) in 1993 may be used to distinguish epidermoid cyst from other possible masses in the testis. Epidermoid cysts may be differentiated from simple and tunica albuginea cysts, which are completely anechoic. Like tumors, granulomatous and chronic inflammatory processes may have a rim or capsule, but they are more likely to have increased vascularity. The lack of enhancement at MR imaging may also help differentiate epidermoid cysts from neoplasms. Abscesses may also have a cystic appearance, although other US findings include irregular borders with increased vascularity of the surrounding parenchyma. On rare occasions, infarction with internal hemorrhage has been described as a solid mass with internal hypoechoic regions (10).
There are several different theories about the embryologic origin of this lesion (9). Metaplasia of the seminiferous epithelium or rete testis has been suggested (1–9), although the prevailing thought has been that the lesion represents monodermal development of a teratoma (1). Price (6) set forth the following guidelines for identifying an intratesticular lesion as an epidermoid cyst: (a) the lesion must be an intraparenchymal cyst, (b) the lumen must contain keratin, (c) the cyst wall should contain fibrous tissue with a complete or incomplete inner lining of squamous epithelium, (d) the cyst must contain no teratomatous components (eg, sebaceous glands, hair), and (e) no scar may be seen in the remaining testicular parenchyma. The presence of teratomatous components and a parenchymal scar signify a burnt-out malignant germ cell tumor. In addition, other pathologists have reported that if testicular intraepithelial neoplasia (carcinoma in situ of the testis) is present in the adjacent tissue, the lesion should be considered a true teratoma and not a benign epidermoid cyst (5).
The management of the lesion has also been controversial, as reflected by the different theories of origin. Formerly, the prevailing thought was that orchiectomy was necessary to arrive at a histologic diagnosis of the lesion. However, there have now been numerous reports that epidermoid cyst can be properly diagnosed on the basis of the specific radiologic features described earlier in a patient with negative tumor markers (
-fetoprotein and ß–human chorionic gonadotropin) and a lesion smaller than 3 cm. In these cases, as long as frozen sections of the lesion demonstrate it to be an epidermoid cyst and two biopsies of the surrounding parenchyma show no testicular intraepithelial neoplasia, the patient may undergo conservative surgery. To our knowledge, no patient with epidermoid cyst who has undergone organ-preserving surgery has had subsequent recurrence, with the longest follow-up being 23 years (2,4,5,7,8).
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References
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- Shah KH, Maxted WC, Chun B. Epidermoid cysts of the testis: a report of three cases and an analysis of 141 cases from the world literature. Cancer 1981; 47:577-582.[CrossRef][Medline]
- Malek RS, Rosen JS, Farrow GM. Epidermoid cyst of the testis: a critical analysis. Br J Urol 1986; 58:55-59.[Medline]
- Dockerty MB, Priestley JT. Dermoid cysts of the testis. J Urol 1942; 48:392-400.
- Heidenreich A, Engelmann UH, Vietsch HV, Derschum W. Organ preserving surgery in testicular epidermoid cysts. J Urol 1995; 153:1147-1150.[CrossRef][Medline]
- Dieckmann KP, Loy V. Epidermoid cyst of the testis: a review of clinical and histogenetic considerations. Br J Urol 1994; 73:436-441.[Medline]
- Price EB, Jr. Epidermoid cysts of the testis: a clinical and pathological analysis of 69 cases from the testicular tumour registry. J Urol 1969; 102:708-713.[Medline]
- Langer JE, Ramchandani P, Siegelman ES, Banner MP. Epidermoid cysts of the testicle: sonographic and MR imaging features. AJR Am J Roentgenol 1999; 173:1295-1299.[Abstract/Free Full Text]
- Malvica RP. Epidermoid cyst of the testicle: an unusual sonographic finding. AJR Am J Roentgenol 1993; 160:1047-1048.[Free Full Text]
- Fu YT, Wang HH, Yang TH, Chang SY, Ma CP. Epidermoid cysts of the testis: diagnosis by ultrasonography and magnetic resonance imaging resulting in organ-preserving surgery. Br J Urol 1996; 78:116-118.[Medline]
- Dogra VS, Gottlieb RH, Rubens DJ, Liao L. Benign intratesticular cystic lesions: US features. RadioGraphics 2001; 21:S273-S281.[Abstract/Free Full Text]
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