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Case Report |
1 Both authors: Department of Radiology, Mayo Clinic Scottsdale, 13400 E Shea Blvd., Scottsdale, AZ 85259.
Received May 19, 2003;
accepted after revision July 14, 2003.
Address correspondence to M. D. Patel.
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An adenomatoid tumor is the most common extratesticular neoplasm [1]. This benign tumor can arise from the epididymis or the testicular tunica. When the mass arises from the tunica vaginalis or tunica albuginea, sonographic findings may distinguish it from a peripheral testicular tumor [2]. There has been limited investigation of the MRI enhancement pattern of testicular tumors, and, to our knowledge, no reports of the MRI features of scrotal adenomatoid tumors. We present a case of an adenomatoid tumor of the tunica albuginea of the testis that underwent preoperative MRI. Our objective is to show the enhancement pattern of this tumor and the effect of the tumor on the signal intensity of the adjacent testicular parenchyma and on the enhancement pattern in the adjacent testicular tunica.
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Sonographic evaluation of the mass revealed a solid-appearing lens-shaped mass in the lower pole of the left testis, relatively hyperechoic to the testicular parenchyma (Fig. 1A). The mass did not bulge the outer contour of the testis. The testicular parenchyma immediately adjacent to the mass showed slightly decreased echogenicity compared with the parenchyma elsewhere. On the basis of the sonographic evaluation, we thought the mass probably arose from the tunica, but we recommended scrotal MRI to verify this impression.
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Scrotal MRI was performed using fast spin-echo T2-weighted images in the sagittal and axial planes; unenhanced and dynamic gadolinium-enhanced gradient-echo T1-weighted images in the axial plane at 30, 60, and 90 sec after contrast administration; and delayed gadolinium-enhanced gradient-echo T1-weighted images in the sagittal and axial planes. The scrotum was elevated between the patient's legs, and images were acquired using a pelvic phased array coil. The peak height of enhancement, defined as the maximal value of the time–signal intensity curve, and the relative percentage of peak height enhancement, defined as (peak height of the area of interest x 100) / (peak height of remote intratesticular parenchyma) were calculated. This method was similar to that described by Watanabe et al. [3].
The unenhanced images showed a lensshaped mass, slightly hypointense to testicular parenchyma, arising from the surface of the testis. A thin band of decreased T2 signal immediately surrounded the entire mass, and a broader, less well-defined zone of decreased T2 signal was seen in the testicular parenchyma immediately adjacent to the tumor (Figs. 1B and 1C). Dynamic and delayed enhanced images revealed that the thin uniform band of hypointense parenchyma around the tumor showed early and persistent enhancement (Figs. 1D and 1E). The mass itself showed internal enhancement less than that of normal testicular parenchyma (relative percentage of peak height enhancement was 67%).
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At left inguinal exploration, the surgeon identified a rock-hard mass on the lower pole of the left testis; the mass was separated completely from the epididymis. A partial orchiectomy was performed to excise the mass and the adjacent seminiferous tubules of the lower pole of the left testis. Pathologic evaluation revealed a well-circumscribed tan nodule measuring up to 1.0 cm in diameter, with histologic features characteristic of a benign adenomatoid tumor of the tunica albuginea, with tunical layers surrounding the entire mass. The adjacent testicular parenchyma showed active spermatogenesis.
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In our patient, MRI findings were useful in suggesting that the palpable mass arose from the tunical surface of the testis rather than from the peripheral seminiferous tubules. The depiction of the thin low-signal well-delineated zone between the mass and the adjacent testicular parenchyma, corresponding to the tunica albuginea, helped to indicate the origin of the mass. The adjacent testicular parenchyma showed poorly defined decreased T2 echogenicity, suggesting a loss of water content. We postulate that this was due to the compressive effects of the tumor. This part of the testis did not show anomalous enhancement characteristics compared with other areas of the testis.
Watanabe et al. [3] have shown that dynamic contrast-enhanced MRI evaluation may be useful in distinguishing testicular tumors from other testicular disorders; in their series, malignant testicular tumors had increased contrast enhancement compared with contralateral normal testicular parenchyma. Other authors have used MRI findings to distinguish benign epidermoid cysts and testicular infarcts from testicular malignant tumors by showing a lack of enhancement of the abnormality [4–6]. In our patient, the adenomatoid tumor itself showed less contrast enhancement than testicular parenchyma remote from the mass and contralateral normal testicular parenchyma. This finding conforms to the prediction of benignity of the mass based on the work of Watanabe et al. However, the adenomatoid tumor did not show an absence of enhancement, in contradistinction to the report of Sadowski et al. [7], which indicated no MRI enhancement of a fibroma of the tunica vaginalis.
The hyperenhancement of the tunica compared with the adenomatoid tumor and testicular parenchyma was a local phenomenon—that is, it was present only in the vicinity of the tumor and was not seen along the tunical layers remote from the mass or in the contralateral testis. We do not know the cause of this local enhancement; it implies some degree of breakdown of normal barriers to the disbursement of gadolinium into the extracellular space, perhaps due to mechanical effects. No pathologic evidence of inflammation was seen around the tumor. Normally, the tunica albuginea does not show contrast enhancement on MRI [8].
This case illustrates the potential value of MRI to further evaluate scrotal disease when sonographic features are inconclusive or unusual. MRI evaluation may provide additional morphologic evidence to allow precise localization of the origin of the mass, may also show contrast-enhancement features that enable further confidence of a benign diagnosis, and may allow conservative management.
Acknowledgments
We thank Ann McCullough for her invaluable assistance with pathologic
review.
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