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Benign Intratesticular Cystic Lesions: US Features1 Vikram S. Dogra, MD ● Ronald H. Gottlieb, MD ● Deborah J. Rubens, MD ● Lydia Liao, MD Benign intratesticular lesions are rare, but recognition is important to avoid unnecessary surgical intervention. The ultrasonographic (US) features that help differentiate benign from malignant intratesticular lesions are emphasized by the authors. Benign lesions include intratesticular simple cysts, tubular ectasia, epidermoid cyst, tunica albuginea cyst, intratesticular varicocele, abscess, and hemorrhage (infarction). US features of cystic malignant neoplasms that help in differentiation of them from benign cystic lesions are also presented. The US appearance of epidermoid cysts varies with the maturation, compactness, and quantity of keratin present. Of the cystic malignant testicular tumors, which can occur anywhere in testicular parenchyma, teratomas are the most frequent to manifest as cystic masses. An abnormal rind of parenchyma with increased echogenicity usually surrounds these lesions. An intratesticular spermatocele communicates with the seminiferous tubules, whereas simple ectasia of the rete testis does not do so directly. These cysts contain spermatozoa and can be septate. The US findings of intratesticular varicocele are similar to those of extratesticular varicocele and include multiple anechoic, serpiginous, tubular structures of varying sizes. Improvements in gray-scale and Doppler US technology allow subtle distinctions between benign and malignant testicular lesions that were not possible a decade earlier.

Index terms: Testis, cysts, 847.31 ● Testis, neoplasms, 847.31 ● Testis, US, 847.12981 ● Varicocele, 847.756 RadioGraphics 2001; 21:S273–S281 1From

the Department of Radiology, University Hospitals of Cleveland, Case Western Reserve University, 11100 Euclid Ave, Cleveland, OH 44106 (V.S.D.); and Department of Radiology, University of Rochester Medical Center, Rochester, NY (R.H.G., D.J.R., L.L.). Presented as an education exhibit at the 2000 RSNA scientific assembly. Received December 28, 2000; revision requested February 15, 2001, and received May 15; accepted May 29. Address correspondence to V.S.D.(e-mail: [email protected]). ©

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Introduction Ultrasonography (US) is the modality of choice for characterization of palpable testicular lesions. Extratesticular lesions are more common than intratesticular ones, and more than 95% of intratesticular lesions are malignant (1). US is associated with a high rate of false-positive findings for malignant testicular neoplasms, which are usually treated by means of radical orchiectomy (2). Nonneoplastic cystic lesions represent a subset of intratesticular lesions of which the majority are benign. It is important for the practicing radiologist and sonographer to recognize this benign subset to prevent unnecessary surgical exploration. This pictorial essay presents the spectrum of intratesticular cystic lesions that can be easily characterized with US.

US Anatomy Relevant anatomic characteristics at US are important for understanding the origin and anatomic location of benign testicular cystic lesions. In the adult, a normal testis is ovoid, measuring approximately 5 ⫻ 3 ⫻ 2 cm, with medium-level echoes. The tunica vaginalis, a fascial structure that envelopes the testicle, has a closely applied visceral layer and an outer parietal layer. The tunica albuginea, a fibrous layer deep to the tunica vaginalis, closely invests the testicle. The posterior surface of the tunica albuginea extends into the interior of the gland, forming an incomplete septum known as the mediastinum testis (Fig 1). In approximately 50% of cases, vessels can be identified within the mediastinum testis by means of color Doppler US (3). Septa extend from the tunica albuginea, dividing the testis into lobules. The lobules contain seminiferous tubules, which open via the straight tubules into dilated spaces called rete testes within the mediastinum. Rete testes in turn communicate via efferent ductules with the epididymal head. The epididymis is

Figure 1. Normal testis in a 38-year-old man. Longitudinal US scan shows the mediastinum testis as an echogenic linear band running across the testis (arrow). If imaged at an angle, the mediastinum testis may resemble a testicular tumor. Most benign cystic testicular lesions occur adjacent to this structure.

composed of a head, body, and tail, the ducts of which continue as the vas deferens in the spermatic cord.

Tunica Albuginea Cysts The pathogenesis of tunica albuginea cysts is not known but believed to be mesothelial. The cysts range from 2 mm to 5 mm in diameter and are brought to medical attention when a patient presents himself for treatment with a palpable lump (4). The mean age at presentation is 40 years, and cysts can even be seen in the 5th and 6th decades. At US, tunica albuginea cysts meet all the criteria of a simple cyst. They characteristically are located at the upper anterior or lateral aspect of the testicle. They can be uni- or multilocular. Sometimes the differentiation of a tunica albuginea cyst from an intratesticular simple cyst or a tunica vaginalis cyst is difficult (Figs 2, 3). Most testicular malignant tumors are palpable, whereas the majority of intratesticular cysts are not palpable except when they are at the periphery of the testis.

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Figures 2, 3. (2) Tunica albuginea cyst in a 34-year-old man. Longitudinal US scan shows a well-defined cystic lesion in the anterior and upper portion of the testis (arrow), a characteristic location for a tunica albuginea cyst. These cysts are usually palpable and seen in a younger population, as opposed to intratesticular simple cysts. (3) Tunica albuginea cyst in an asymptomatic 70-year-old man who had a palpable left testicular mass. Longitudinal US scan shows a well-defined cyst with an imperceptible wall, an anechoic center, and through transmission. A diagnosis of intratesticular cyst was advanced. Findings of tumor markers were negative, but because the mass was palpable, the urologist suspected a malignant tumor. The patient underwent radical orchiectomy, after which a tunica albuginea cyst was confirmed. When large, these cysts can compress the testicular parenchyma, making distinction from an intratesticular cyst difficult, as in this case.

Simple Cysts

Figure 4. Simple intratesticular cyst in a 61year-old man. A testicular mass was found at an annual physical examination. Findings of tumor markers were negative. Longitudinal US scan of the left testis shows two intratesticular cysts that meet all the US criteria of a simple cyst. Testicular microliths surround the cysts. The case was followed on a yearly basis for 5 years, with no change.

Simple cysts are detected incidentally and occur in men 40 years of age and older. Their size is variable and can range from 2 mm to 2 cm in diameter. The cysts are usually solitary, but they can be multiple. Simple cysts can occur anywhere in the testis but are often near the mediastinum testis and are associated with extratesticular spermatoceles. Simple testicular cysts are usually not palpable and, even when large, are not firm. This latter characteristic distinguishes them from tunica albuginea cysts, which are very firm, even when small. At US, simple cysts have an imperceptible wall, an anechoic center, and through transmission (5) (Fig 4). Hamm et al (6) stress the importance of palpability and claim that palpable intratesticular cysts should be removed. This recommendation would include simple cysts if they were palpable. However, Hamm et al reported that all of their cystic neoplasms (13 of 16, excluding three epidermoid cysts) except one had

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Figure 5. Intratesticular epidermoid in a 22-year-old man. A preemployment physical examination revealed a palpable, nontender mass at the inferior pole of the left testis. Findings of tumor markers were negative. Longitudinal US scan shows a well-circumscribed heterogeneous mass with an echogenic rim (arrow). Color Doppler US examination revealed no vascularity within the mass. At histopathologic examination, the echogenic rim corresponded to keratin deposition.

US features of complicated cyst. They did not encounter a cyst that appeared simple at US, was palpable, and turned out to be a neoplasm. Simple cysts require no treatment. Proposed causes for simple cysts include trauma, surgery, and prior inflammation. Cystic teratomas may manifest as a cystic mass; however, their usual appearance is that of an inhomogeneous mass containing cystic and solid areas of various sizes (7), which helps differentiate them from simple cysts.

Epidermoid Cysts Uncommon benign tumors of germ cell origin that are also known as keratocysts, epidermoid cysts range in diameter from 1 cm to 3 cm. They are nontender and usually palpable. The patient’s age at presentation is variable but usually ranges from 20 to 40 years. The US appearance varies with the maturation, compactness, and quantity of keratin present within the epidermoid cyst. A

Figure 6. Intratesticular epidermoid in a 21-year-old man, who presented with a growing mass in the left testis of 2–3 months duration. Physical examination revealed a 2- to 3-mm-diameter, palpable, nontender, firm nodule on the surface of the left testicle. (a) Longitudinal US scan reveals a well-circumscribed hypoechoic mass with a concentric lamellar pattern of alternating hyper- and hypoechoic rings (arrow). This US pattern is referred to as the onion ring appearance and is characteristic of an epidermoid cyst. At US, these cysts appear solid because of the high acoustic impedance of their contents. (b) Photomicrograph (original magnification, ⫻40) of an epidermoid cyst shows concentric layers of keratin (arrow), which correspond to the concentric, lamellar pattern seen at US.

target appearance, a solid mass with an echogenic rim (Fig 5), and a characteristic “onion ring” configuration with alternating layers of hyper- and hypoechogenicity (Fig 6) have been described

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Figures 7, 8. (7) Mild cystic transformation of the rete testis (tubular ectasia) in a 52-year-old man. Longitudinal US scan of the right testis shows multiple avascular circular structures of varying sizes in the posterolateral region. There was an associated spermatocele (not shown). The patient was uncomfortable from the spermatocele and underwent spermatocelectomy. (8) Moderate (a) and severe (b) cystic transformation of the rete testis (tubular ectasia) in a 70-year-old man who presented with palpable masses in both testes. (a) Longitudinal US scan of the left testis shows anechoic, multiple tubular lesions in the superolateral region near the mediastinum testis, with no evidence of flow at Doppler US interrogation. An associated spermatocele was in the head of the epididymis. (b) Longitudinal US scan of the right testis reveals avascular, anechoic dilated channels in the posterolateral region of the testis. There was an associated spermatocele. Tubular ectasia is a benign condition usually associated with spermatoceles (as in this case), is commonly bilateral, and requires no follow-up.

(8). These cysts do not show blood flow at Doppler US examination. The constellation of an onion ring configuration, negative tumor marker status, and avascularity helps differentiate testicular epidermoids from other germ cell tumors (9). If the diagnosis of an epidermoid is suspected at preoperative US, the lesion can be enucleated and frozen sections obtained to confirm the diagnosis. This procedure avoids the need for orchiectomy.

Cystic Transformation of the Rete Testis This benign condition, also known as tubular ectasia, results from partial or complete obliteration of the efferent ductules, which causes ectasia and, eventually, cystic transformation. These cysts can

be identified at US as fluid-filled tubular structures (Figs 7, 8). Most occur in men older than 55 years, and the process is frequently bilateral (10) but is often asymmetric. The diagnosis can still be made with confidence when the process is unilateral. The location of the lesion in or adjacent to the mediastinum testis and the presence of epididymal cysts are characteristic. The key to the diagnosis of this condition is the elongated shape that replaces the mediastinum. These features aid in distinguishing cystic transformation of the rete testis from cystic malignant testicular tumors (which can occur anywhere in testicular parenchyma) (11). Teratomas are the most frequent to

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Figures 9, 10. (9) Testicular immature teratoma that manifested as a cystic mass in a 23-yearold man. Sagittal US scan of the left testis reveals multiple cystic areas within the testicle ranging from 2 mm to 15 mm in diameter. This process involves nearly the whole testis. The patient underwent radical orchiectomy, which confirmed the diagnosis of immature teratoma. These cystic changes can be easily differentiated from tubular ectasia, which is confined to the mediastinum and occurs in an older population. (10) Mixed nonseminomatous germ cell tumor that manifested as a cystic lesion in a 36-year-old man who presented with testicular enlargement and pain of 2 months duration. Sagittal US scan of the right testicle shows multiple cystic regions surrounded by a rim of hyperechoic testicular parenchyma distinct from the normal testicular parenchyma. Color and duplex Doppler US did not show any blood flow in the cystic areas but did show flow in the tumor stroma surrounding these cystic areas. The patient underwent orchiectomy, which confirmed the diagnosis.

manifest as cystic masses (Fig 9); however, a cystic tumor is rare, and when present, cystic tumors do not meet all the criteria of a simple cyst. Usually, an abnormal rind of parenchyma with increased echogenicity surrounds cystic malignant tumors (Fig 10). The age of the patient, clinical presentation, and tumor marker status allow diagnosis of a tumor with fair certainty.

Intratesticular Spermatocele An intratesticular spermatocele is a cystic intraparenchymal lesion that is attached to the mediastinum in the area of the rete testis. It communicates with the seminiferous tubules, whereas simple ectasia of the rete testis does not directly do so (12). These cysts contain spermatozoa and can be septate (Fig 11).

Figure 11. Intratesticular spermatocele in a 38-yearold man with a palpable testicular mass found during evaluation for infertility. Transverse US scan shows a cystic lesion 1.3 cm in its greatest dimension that has all the features of a simple cyst except that its wall is slightly irregular. Findings of tumor markers were negative. Because the mass was palpable and the patient was older, inguinal exploration was performed. Examination of frozen sections helped confirm that the mass was an intratesticular spermatocele with mature spermatozoa as its contents. US features of such spermatoceles are usually indistinguishable from those of a simple cyst.

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Figure 12. Intratesticular varicocele in a 47-year-old man. (a) Longitudinal US scan of the left testis shows intratesticular tubular cystic structures of varying sizes. (b) Color Doppler US scan (shown in black and white) shows flow (arrow) within the tubular structures. (c) Pulse Doppler US scan shows increased flow (arrow) with the Valsalva maneuver, a finding characteristic of venous flow. The patient also had an associated extratesticular varicocele (not shown).

Intratesticular Varicocele The pathogenesis and clinical implications of this newly defined entity are not yet well established. Intratesticular varicoceles can occur in association with extratesticular varicoceles, but their independent existence is more common (13). Patients with this condition may have pain related to passive congestion of the testis, which eventually stretches the tunica albuginea. The US findings of intratesticular varicocele are similar to those of extratesticular varicocele and include multiple

anechoic, serpiginous, tubular structures of varying sizes. Color flow and duplex Doppler US show a venous flow pattern with a characteristic venous spectral waveform, which increases with the Valsalva maneuver (14) (Fig 12). The main differential diagnosis is a pseudoaneurysm, which has a characteristic yin-and-yang flow pattern (15), distinct from the venous flow of a varicocele.

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Figure 13. Testicular abscess in a 38-year-old man. (a) Longitudinal US scan shows a complex hypoechoic mass with an irregular margin. There is no through transmission, but there is a small, associated, reactive hydrocele and skin thickening. (b) Color Doppler US scan (shown in black and white) reveals increased vascularity in the surrounding parenchyma. The patient had orchitis, which led to abscess formation.

Figure 14. Infarction and hemorrhage in a 31-year-old man. (a) Longitudinal US scan shows an oblong, intratesticular, complex cystic lesion with areas of central necrosis. (b) Transverse US scan shows irregular, shaggy walls with low-level internal echoes and no through transmission. At US, this lesion was believed to represent an abscess, but at orchiectomy, it was confirmed to be an area of infarction with central necrosis. No abscess was found.

Intratesticular Abscess These abscesses are usually secondary to epididymo-orchitis; other causes include trauma, testicular infarction, and mumps. Their US features include shaggy, irregular walls, intratesticu-

lar location, low-level internal echoes, and occasionally, hypervascular margins (Fig 13).

Intratesticular Infarction Focal intratesticular infarction usually manifests as a hypoechoic mass that is largely avascular. Hemorrhagic necrosis is uncommon, and must be investigated further to exclude a diagnosis of a tumor or abscess (Fig 14).

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Conclusions This pictorial essay reinforces and advances the necessary knowledge base required by a radiologist to correctly identify benign intratesticular cystic lesions and differentiate them from malignant testicular lesions, with the goal being to prevent unnecessary surgical intervention. Improvements in gray-scale and Doppler US technology allow subtle distinctions between benign and malignant testicular lesions that were not possible a decade earlier. Acknowledgments: The authors acknowledge Donna Drews, Margaret Kowaluk, and Theresa Kubera for their assistance with the exhibit.

References 1. Moghe PK, Brady AP. Ultrasound of testicular epidermoid cysts. Br J Radiol 1999; 72:942–945. 2. Tackett RE, Ling D, Catalona WJ, Melson GE. High resolution sonography in diagnosing testicular neoplasms: clinical significance of false positive scans. J Urol 1986; 135:494 – 496. 3. Middleton WD, Bell MW. Analysis of intratesticular arterial anatomy with emphasis on transmediastinal arteries. Radiology 1993; 189:157–160. 4. Martinez-Berganza MT, Sarria L, Cozcolluela R, Cabada T, Escolar F, Ripa L. Cysts of the tunica albuginea: sonographic appearance. AJR Am J Roentgenol 1998; 170:183–185. 5. Gooding GA, Leonhardt W, Stein R. Testicular cysts: US findings. Radiology 1987; 163:537–538.

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6. Hamm B, Fobbe F, Loy V. Testicular cysts: differentiation with US and clinical findings. Radiology 1988; 168:19 –23. 7. Dambro TJ, Stewart RR, Barbara CA. The scrotum. In: Rumack CM, Wilson SR, Charboneau JW, eds. Diagnostic ultrasound. 2nd ed. St Louis, Mo: Mosby, 1998; 791– 821. 8. 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. 9. Dogra VS, Gottlieb RH, Rubens DJ, Oka M, Di Sant Agnese AP. Testicular epidermoid cysts: sonographic features with histopathologic correlation. J Clin Ultrasound 2001; 3:192–196. 10. Tartar MV, Trambert MA, Balsara ZN, Mattrey RF. Tubular ectasia of the testicle: sonographic and MR imaging appearance. AJR Am J Roentgenol 1993; 160:539 –542. 11. Bree RL, Hoang DT. Scrotal ultrasound. Radiol Clin North Am 1996; 34:1183–1205. 12. Yalowitz BR, Eble JN, Wilks DC. Spermatozoacontaining simple cysts of the rete testis. J Urol 1989; 142:1572–1573. 13. Das KM, Prasad K, Szmigielski W, Noorani N. Intratesticular varicocele: evaluation using conventional and Doppler sonography. AJR Am J Roentgenol 1999; 173:1079 –1083. 14. Mehta AL, Dogra VS. Intratesticular varicocele. J Clin Ultrasound 1998; 26:49 –51. 15. Dee KE, Deck AJ, Waitches GM. Intratesticular pseudoaneurysm after blunt trauma. AJR Am J Roentgenol 2000; 174:1136.