Epididymal cyst/spermatocele. Longitudinal ultrasonographic image showing an anechoic lesion with well-defined margins in the head of the epididymis (asterisk)
Very large epididymal cysts may occasionally be difficult to differentiate from hydroceles. However, cysts displace the testis, whereas hydrocele envelops it.
39.3 Cysts of the Tunica Albuginea
Tunica albuginea cysts typically manifest as small palpable masses, single or multiple, mimicking clinically a testicular neoplasm. Most commonly, they are along the upper anterior or lateral aspect of the testicle. The diagnosis is usually straightforward at ultrasound (Fig. 39.2) which shows a small, peripherally located, anechoic lesion within the layers of the tunica meeting all the criteria of a simple cyst [2–4]. The presentation with internal echoes or complex appearance raising concern for a neoplasm is very rare.
Tunica albuginea cyst. Small, anechoic, palpable mass along the anterior aspect of the testis within the layers of the tunica albuginea (arrowhead)
Occasionally, very small cysts may be difficult to identify. Combined ultrasound and palpation allow their identification in virtually all cases (Fig. 39.3). On the other hand, large cysts of the tunica albuginea may grow compressing the testicular parenchyma and simulating an intratesticular cyst (Fig. 39.4).
Very small cyst of the tunica albuginea. Patient presented with a small palpable testicular lesion which was not initially identified on ultrasonography. Repeated investigation combined with palpation allows immediate identification of the palpable lesion which is characterized as a small cyst of the tunica albuginea (arrowhead). F finger of the sonologist
Large cyst of the tunica albuginea (asterisk) compressing the testicular parenchyma and simulating an intratesticular cyst
39.4 Simple Testicular Cysts
Intratesticular cysts are usually non-palpable and thus detected incidentally. Similar to cysts elsewhere in the body, they are usually well defined and anechoic with an imperceptible wall (Fig. 39.5) [1–4]. Testicular cysts are usually solitary, but can be multiple, often associated with extratesticular spermatoceles. Simple testicular cysts can be categorized as benign. No treatment is required . They can occur anywhere in the testis but are often near the mediastinum.
Simple testicular cyst. Small non-palpable incidentally detected anechoic lesion within the testis (asterisk)
39.5 Complex Testicular Cysts
When a cyst does not fulfill the typical criteria of a simple cyst because of intracystic content, septa, or vegetations, a cystic neoplasm must be ruled out [1, 6]. Content mobilization allows diagnosis of debris, and the presence of color signal is diagnostic for vegetation. Intracystic amorphous content, however, is often not mobile, and the absence of flows at color Doppler interrogation is not sensitive enough to rule out vegetations. Complex testicular cysts often reduce in complexity and size or disappear during the follow-up, revealing their benign nature (Fig. 39.6). CEUS is of help showing avascular cystic content in complex benign cysts, while virtually all tumors with cystic components, enclosed mature teratomas, display intralesional vascularization after microbubble contrast injection .
Complex testicular cyst containing echogenic debris (arrowhead). The cyst disappeared during the follow-up (not shown)
39.6 Epidermoid Cysts
Epidermoid cysts are benign germ cell lesions that often present with a characteristic ultrasonographic pattern and can be correctly diagnosed preoperatively. They are true cysts with a well-defined fibrous wall containing a variable quantity of keratinizing, stratified epithelium. Their pathogenesis is uncertain: epidermoid cysts may result from monodermal development of a teratoma or due to squamous metaplasia of surface mesothelium. When an epidermoid cyst is suspected at imaging, testicular-sparing surgery and intraoperative pathological analysis are suggested. The ultrasonographic appearance of epidermoid cysts varies with the maturation, compactness, and quantity of keratin present [2, 3, 8]. Four ultrasonographic appearances have been described: type 1, classic “onion-ring” appearance with alternating hyperechoic and hypoechoic layers; type 2, densely calcified mass with an echogenic rim; type 3, cyst with a rim and either peripheral or central calcification; and type 4, mixed pattern, heterogeneous and poorly defined (Fig. 39.7). Occasionally, epidermoid cyst may resemble a simple cyst or a minimally complicated cyst with slightly inhomogeneous content and echogenic rim. Regardless of their appearance, they are hard at elastography, and intralesional vascularization is lacking both on color Doppler and CEUS modes [6, 9].
Epidermoid cysts. (a) The lesion is avascular at color Doppler interrogation. It shows thin wall and relatively echogenic content with onion-ring appearance. (b) Another patient with epidermoid testicular cyst showing parietal and internal calcifications
The appearance of epidermoid cysts on gray-scale ultrasonography is often characteristic, but not pathognomonic. Teratoma and other tumors must be ruled out. Care must be taken for possible signs of malignancy such as any intralesional flow, irregular borders, or irregularities within the surrounding testicular parenchyma. Negative tumor markers increase diagnostic confidence.
39.7 Cystic Tumors
The presence of cystic components in testicular tumors is common. Tumors with prevailing cystic component, however, are rare [2, 8]. If a cystic lesion has any internal complexity, it must be considered a tumor, until its benign nature is demonstrated. Differential diagnosis between cystic tumors and benign complex cysts may be occasionally difficult based on conventional ultrasonographic modes only, as solid components often lack vascularization on color Doppler interrogation. CEUS eases the differential diagnosis, showing in virtually all tumors the vascularization of the solid components.
39.8 Tubular Ectasia of the Rete Testis
Dilatation of the rete testis is very common, often bilateral, and mostly seen in patients over 50 years of age. It can be associated with either postinfectious, post-traumatic, or post-prostatectomy epididymal obstruction. Possible contributing factors include epididymitis, testicular biopsy, and vasectomy. Epididymal abnormalities such as spermatoceles or dilated efferent ducts are frequently associated.
At ultrasonography the dilated rete testis presents with multiple, low-reflective, oval, or rounded structures within the mediastinum testis (Fig. 39.8) lacking vascularization on Doppler and contrast-specific modes [1, 3, 10].