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Original Report |
1
Department of Diagnostic Radiology, School of Medicine, Yeungnam University,
317-1, Daemyungdong, Namgu, Taegu, 705-717, South Korea.
2
Department of Diagnostic Radiology, School of Medicine, Keimyung University,
194, Dongsandong, Junggu, Taegu, 700-712, South Korea.
Received May 2, 2001;
accepted after revision September 12, 2001.
Address correspondence to J-H. Cho.
Abstract
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CONCLUSION. Sonographic findings of a markedly heterogeneous intratesticular mass with or without alternating hypo- and hyperechoic layers surrounded by a hypoechoic or echogenic rim and the absence of flow on color Doppler sonography suggest the preoperative diagnosis of testicular epidermoid cysts. T2-weighted MR imaging findings of a high-signal-intensity mass with or without low-signal-intensity foci surrounded by a low-signal-intensity rim and the absence of enhancement on contrast-enhanced T1-weighted MR images can strengthen the preoperative diagnosis. These imaging findings can offer a basis for surgeons to attempt testis-sparing surgery instead of orchiectomy.
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Epidermoid cysts are benign lesions with no malignant potential [3] and can be cured by orchiectomy or enucleation of the lesion [3, 4]. However, many surgeons still favor orchiectomy rather than enucleation because sonographic findings are not specific and cannot accurately differentiate the lesions from testicular malignancies. Therefore, if sonography does not show specific findings compatible with testicular epidermoid cysts, an additional study is needed for confirmation of the diagnosis.
We attempted to identify the findings necessary to accurately diagnose a testicular epidermoid cyst by analysis of sonographic and MR imaging findings.
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All five patients underwent preoperative sonography using 5- to 10-MHz linear transducers and MR imaging examinations.
An Ultramark 9 HDI scanner (Advanced Technology Laboratories, Bothell, WA) was used in four patients, and a Sequoia scanner (Acuson, Mountain View, CA) was used in one patient. Color Doppler sonography was performed in three of the five patients. On sonography, the sharpness of the margin, echogenicity of the wall, internal echo texture, and flow signal of the mass were evaluated.
The MR imaging examinations were performed using a 1.5-T scanner (Magnetom Vision; Siemens, Erlangen, Germany) with a surface coil by a standard scrotal imaging protocol [5]. Contrast-enhanced MR imaging was performed in all five patients after IV administration of 0.1 mmol/kg of gadopentetate dimeglumine. In one patient, a dynamic enhanced study was performed, and images were obtained at 30, 90, 180, and 300 sec after IV injection of the contrast material. The signal intensities on the T1- and T2-weighted MR images, margin of the mass, capsule, and contrast enhancement pattern were evaluated.
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-fetoprotein levels were
normal, and there were no other specific laboratory findings.
Pathologic Features
All lesions were intraparenchymal and sharply demarcated. Adjacent
testicular tissue was compressed but otherwise unremarkable in all patients.
The cysts ranged from 1.1 x 1.0 to 3.0 x 2.5 cm. All of the cysts
were unilocular masses lined by a mature squamous epithelium and filled with
laminated keratinous materials. In one patient, calcification and reactive
osseous metaplasia were found focally.
Sonographic Features
On sonography, four lesions were sharply demarcated, and the fifth showed a
focally indistinct margin (Fig.
1A). Three lesions were surrounded by a hypoechoic rim (Figs.
1A,
2A, and
3A) and two by an echogenic rim
(Fig. 4A). All lesions showed
a markedly heterogeneous internal echotexture. One of the lesions contained a
focal echogenic portion with posterior sonic shadowing
(Fig. 2A). Three lesions showed
an internal pattern of alternating hypo- and hyperechoic layers. One lesion
showed an onionskin appearance (Fig.
3A), one showed a target appearance
(Fig. 4A), and one showed a
laminated appearance (Fig. 2A).
The remaining two lesions showed heterogeneous mixed echogenicity with no
alternating pattern (Fig. 1A).
Vascular flow signal was not seen on color Doppler sonography
(Fig. 3A).
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MR Imaging Features
On T2-weighted MR imaging, all lesions were surrounded by a
low-signal-intensity rim and were sharply marginated. In one patient, a small
part of the margin was indistinct (Fig.
1B). Four lesions were heterogeneously higher in signal intensity
than that of normal testicular parenchyma (Figs.
1B,
2B, and
4B), and one lesion was
homogeneously high in signal intensity
(Fig. 3B). One out of five
lesions showed a typical target appearance
(Fig. 4B).
(Fig. 3B). On T1-weighted MR
images, four lesions were homogeneous or heterogeneous, with low signal
intensity containing intermediate- or high-signal-intensity portions
(Fig. 4C); and in the
remaining one lesion, low, intermediate, and high signal intensities were
intermixed (Fig. 1C). On
contrast-enhanced images, all lesions were sharply demarcated
low-signal-intensity masses, and contrast enhancement was not seen in any of
the cases (Figs. 1D and
3C).
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Because testicular epidermoid cysts are benign, a cure is possible if the mass is completely resected. Recently, organ-preserving surgery has become favored over traditional inguinal orchiectomy because it may offer better psychologic and cosmetic results and the preservation of fertility. Although organ-preserving surgery has been widely advocated, many surgeons still carry out an orchiectomy because of the relatively high incidence of malignant testicular masses, the potential for misdiagnosis on frozen sections, and the possible existence of concurrent malignant lesions. But the most important problem is that the exact preoperative differential diagnosis is difficult.
Sonography can suggest an epidermoid cyst, but it is often not sufficient to convince surgeons that the mass is an epidermoid cyst. Heidenreich et al. [4] reported that the sonographic appearance was not specific and inguinal testicular exploration was required. However, if an exact preoperative imaging diagnosis is possible, organ-preserving surgery may be carried out more often.
Sonographic findings of epidermoid cysts vary, but some suggestive findings have been described, and these correlate well with the gross pathologic findings [6,7,8,9,10,11]. Testicular epidermoid cysts are well demarcated from surrounding normal parenchyma by an echolucent or echogenic rim. Pathologically, the cyst is lined by a complete or incomplete inner lining of squamous epithelium. Also, a fibrous capsule with or without calcification or ossification may be present [7,8,9,10]. Langer et al. [10] found that the lesions with an echogenic rim had a fibrous capsule without calcification, and the lesions without an echogenic rim had an outer lining composed only of squamous epithelium. However, other investigators [8, 9] found that the echogenic rim represented calcification. On pathologic correlation of our study, two cases with an echogenic rim had fibrous capsules, and one of them showed a rim of calcification. A focally indistinct margin seen in one case was proved to have only a squamous epithelium without a fibrous capsule. The internal echogenicity may vary depending on the complexity of the internal contents. However, some cases show the specific finding of an onionskin [7, 10] or target [11] appearance of concentric rings of alternating hypoechogenicity and hyperechogenicity. The sonographic finding of alternating layers is pathologically well correlated with alternating layers of compacted keratin and loosely dispersed desquamated squamous cells [3, 7, 10]. Our cases also showed varying internal echogenicity. This complexity seems to be caused by the difference of arrangement in alternating patterns. In the cases of regularly arranged alternating patterns, an onionskin or target appearance is present; in the cases of somewhat irregularly arranged alternating patterns, a laminated appearance is seen; and in the cases of random arrangement with no or few alternating patterns, the lesions appear as merely heterogeneous masses.
Langer et al. [10] described a lack of internal vascularity as another feature that can differentiate epidermoid cysts from most solid intratesticular lesions. Our study correlated well with the results of Langer et al. All three lesions examined with color Doppler sonography did not show any internal flow signal.
Few reports have been published in English describing the MR imaging findings of testicular epidermoid cysts [2, 5, 6, 10, 12]. Four of them were case reports, and another study described the MR imaging findings of only three cases [10]. In these reports, the researchers found that testicular epidermoid cyst showed a bull's-eye or target appearance or signal intensity characteristics more typical of a cystic lesion. The target appearance was composed of a low-signal-intensity center, a high-signal-intensity mid zone, and a peripheral low-signal-intensity rim on both T1- and T2-weighted MR images. The researchers postulated that the outer fibrous capsule, epithelial lining, and adjacent compact keratin produced peripheral low signal intensity; the dense debris and calcification produced central low signal intensity; and the desquamated cellular debris containing both a high water content and a high lipid content produced mid zone of high signal intensity on both T1- and T2-weighted MR images. In our study, the high-signal-intensity portion correlated with desquamated cellular debris containing both high water and lipid contents, and the low-signal-intensity focus correlated with dense keratin debris. One case seen with an onionskin appearance on sonography showed a homogeneous high-signal-intensity mass on the T2-weighted MR image. This result did not correlate with the report of Langer et al. [10] that two out of three cases showed an onionskin appearance on both MR imaging and sonography. We believe this difference was caused by the resolution of MR imaging being insufficient to discriminate the thin layers of laminated keratin debris. In addition, intervening water and lipid content were relatively abundant in our case.
To our knowledge, only one report of contrast-enhanced MR imaging of epidermoid cysts has been published in English [10]. In this report, the researchers performed contrast studies that did not show enhancement in two patients. This is well correlated with our result that showed no enhancement in all of the patients. No enhancement on contrast-enhanced MR imaging was well correlated with the results of color Doppler sonography. It may be a useful finding to differentiate epidermoid cysts from other solid intratesticular lesions.
We summarize the radiologic findings of testicular epidermoid cyst as a lesion with a typical onionskin or target appearance, a markedly heterogeneous solid-appearing lesion surrounded by a hypo- or hyperechoic rim with sharp margins on sonography, a high-signal-intensity mass containing low- or medium-signal-intensity foci surrounded by a low-signal-intensity rim, and a lack of vascularity on Doppler sonography or enhanced MR imaging.
However, our study has several limitations. The number of lesions in our study was not sufficient to represent the entire spectrum of testicular epidermoid cysts. Also, we could not present the specific imaging findings able to differentiate epidermoid cysts from other solid testicular tumors, including testicular malignancy.
In conclusion, sonographic and MR imaging findings may suggest a testicular epidermoid cyst. Although sonography shows strongly suggestive findings of epidermoid cyst, sonography is not completely diagnostic. In this situation, MR imaging, including contrast enhancement, may provide more supportive findings for the diagnosis of an epidermoid cyst, and this may lead surgeons to perform organ-preserving surgery instead of orchiectomy.
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