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Spermatic Cord and Testicular Adnexa
Introduction
The paratesticular region includes the testicular tunics, efferent ductules, epididymis, spermatic cord, and vas deferens. Most studies of paratesticular region pathology include the rete testis despite its intratesticular location. Numerous rare and interesting lesions arise in this region, including cysts, “celes,” inflammatory diseases, embryonic remnants, neoplasms, and neoplasm-like proliferations ( Table 14.1 ). In children, one of the common neoplasms is paratesticular rhabdomyosarcoma. In adults the most common pathologic conditions, in order of frequency and excluding “celes,” are epididymitis, lipoma of the spermatic cord, adenomatoid tumor of the epididymis, and sarcoma of the spermatic cord.
Table 14.1
Paratesticular Tumors and Cysts in the Ccanadian Reference Center for Cancer Pathology, 1949 to 1986
From Srigley JR, Hartwick RWH. Tumors and cysts of the paratesticular region. Pathol Annu 1990:25(Pt 2):51–108 (review), with permission.
| Diagnosis | No. of Cases |
|---|---|
| Cysts | |
| Mesothelial cyst | 4 |
| Epididymal cyst | 1 |
| Benign Neoplasms and Pseudotumors | |
| Adenomatoid tumor | 23 |
| Nodular and diffuse fibrous proliferation | 6 |
| Leiomyoma | 6 |
| Cystadenoma of epididymis | 3 |
| Hamartoma of rete testis | 1 |
| Adenomatous hyperplasia of epididymis | 1 |
| Adenomatous hyperplasia of rete testis | 1 |
| Mixed gonadal stromal tumor | 1 |
| Adrenal cortical heterotopia | 1 |
| Rhabdomyoma | 1 |
| Miscellaneous soft tissue tumors | 8 |
| Malignant Neoplasms | |
| Primary | |
| Rhabdomyosarcoma | 14 |
| Liposarcoma | 9 |
| Leiomyosarcoma | 7 |
| Malignant mesothelioma | 7 |
| Malignant fibrous histiocytoma | 3 |
| Malignant mesenchymoma | 1 |
| Plasmacytoma | 1 |
| Papillary serous cystadenocarcinoma of low malignant potential | 1 |
| Sarcoma, not otherwise specified | 3 |
| Secondary | |
| Metastatic carcinoma | 4 |
| Metastatic carcinoid tumor | 2 |
| Metastatic non-Hodgkin lymphoma | 2 |
It is often difficult to diagnose paratesticular masses before or during surgery due to their varied morphologic appearance and rarity. An inguinal surgical approach is usually indicated when there is a suspicion of malignancy. The pathologist should document the anatomic site of origin, histologic classification, and extent of spread of the lesion.
Embryology and Normal Anatomy
The paratesticular region contains numerous anatomically complex epithelial and mesenchymal structures, often within embryonic remnants ( Fig. 14.1 ). The rete testis of the mediastinum of the testis, the first element of the wolffian collecting system, connects the seminiferous tubules and efferent ductules.
The most common abnormalities of the paratesticular region are benign, including hydrocele, lipoma, and inflammatory conditions such as epididymitis, but a variety of cystic and proliferative lesions also occur and are diagnostically challenging.
Embryology
The embryology of the testis and its adnexa is described in Chapter 12 ; herein is a brief summary of significant events in the development of paratesticular tissues. The testis and head of the epididymis arise from the genital ridge. The wolffian ducts, the male genital ducts, are paired tubes that are associated with the developing gonads and degenerating mesonephric tubules. The body and tail of the epididymis, the vas deferens, and the ejaculatory duct arise from the mesonephric tubules; other degenerating tubules often persist as embryonic remnants including the appendix epididymis, paradidymis, and cranial and caudal aberrant ductules ( Fig. 14.1 ). The paired vasa deferentia connect to the ejaculatory ducts within the prostate that, in turn, have their outlets in the prostatic urethra adjacent to the müllerian tubercle. Blind diverticula of the distal vas deferens form the seminal vesicles. The müllerian duct, or paramesonephros, regresses in men but may persist as embryonic remnants such as the appendix testis and prostatic utricle.
Anatomy
Scrotum and Testicular Tunics
The sac of the scrotum is divided by a partial median septum into two compartments, each of which contains a testis and epididymis and the lower portion of the spermatic cord. The scrotal wall consists of six layers, from the inside outward: the tunica vaginalis, the internal spermatic fascia, the cremasteric muscle, the external spermatic fascia, the dartos muscle, and the skin. The tunica vaginalis is a thin mesothelium-covered layer of the parietal peritoneum that also covers the white fibrous tunica albuginea of the testis and epididymis; it is initially in contact with the peritoneal cavity from which it arises but becomes isolated with regression of the processus vaginalis. A common stimulus such as androgens is likely required for obliteration of the processus vaginalis and epididymal development, a hypothesis supported by the common coexistence of epididymal anomalies and patency of the processus vaginalis.
The internal spermatic fascia is a continuation of the transversalis fascia, and the external fascia is a continuation of the external oblique aponeurosis. The cremasteric muscle consists of incomplete slips of muscle, usually in the upper part of the scrotal wall. The dartos muscle consists of smooth muscle embedded in loose areolar tissue. The scrotum is supplied by the external and internal pudendal, cremasteric, and testicular arteries. Lymphatics drain to the superficial inguinal lymph nodes.
Rete Testis
The rete testis is formed by the convergence of the seminiferous tubules (see Chapter 12 ). The tubules follow a cranial and dorsal course through the fibrous connective tissue of the mediastinum testis, eventually merging into 12 to 20 ducts (the efferent ductules, or ductuli efferentes that perforate the tunica vaginalis and form the head of the epididymis at the upper pole of the testis). After puberty, elastic fibers are present in the muscular coat of the ductules, epididymis, and vas deferens.
Epididymis
The epididymis is a highly convoluted tubule that is attached to the dorsomedial portion of the testis, connecting the efferent ductules of the rete testis with the vas deferens. It is about 6 m long. The head consists of a series of conical masses, the lobules, each of which contain a single duct measuring 15 to 20 cm long; it is lined by tall columnar epithelium and invested with a thick layer of smooth muscle. The body of the epididymis is a single highly convoluted tube that increases in diameter distally to form the tail. The tail distally merges with the vas deferens.
Development of the efferent ducts and ductus epididymis follows a biphasic pattern. Progressive development occurs from the fetal period to infancy between 2 and 4 months of age, but this development is transient and regresses during later infancy. At childhood, definitive development is initiated and finishes at puberty. These changes are probably related to the androgen dependence of the epididymis, the different stages of testicular maturation, and the steroidogenic activity of the Leydig cells. The epididymis plays a critical role in maturation and viability of spermatozoa; SED1 facilitates epididymal cell adhesion, and its loss leads to breakdown of the epididymal epithelium and consequent development of spermatic granulomas.
A variety of morphologic variations occur in the epididymal columnar cells and vas deferens including cribriform hyperplasia (42% of patients), patchy or diffuse eosinophilic granular cell change (Paneth cell–like metaplasia) (8.3%), intranuclear eosinophilic inclusions, nuclear atypia with “monstrous” cells (14%), adenomatous hyperplasia, prostatic-type glands, epithelial luminal pitting, multiple diverticula in the cauda epididymis in the elderly, and accumulation of lipofuscin pigment.
Vas Deferens (Ductus Deferens) and Spermatic Cord
The vas deferens is about 46 cm long, traversing the spermatic cord and inguinal canal to connect the tail of the epididymis with the ejaculatory ducts. In the spermatic cord, it is invested with a thick, muscular coat that includes the internal spermatic, cremasteric, and external spermatic fasciae; other structures of the spermatic cord include the pampiniform plexus, the testicular artery, lymphatics, and nerves. Upon exiting the spermatic cord, the vas deferens passes extraperitoneally upward, and laterally in the pelvis, then medial to the distal ureter and the posterior wall of the bladder, and terminates at an acute angle in a dilated ampulla that, with the duct of the seminal vesicle, forms the ejaculatory duct. The vas deferens is supplied by its own artery, the artery of the vas deferens, which is usually a branch of the internal iliac or umbilical artery.
The vas deferens is lined by columnar epithelium in low folds, with morphologic variations like those in the epididymis (see earlier). The wall of the vas deferens consists of three layers of smooth muscle: the inner longitudinal, middle circular, and outer longitudinal layers. Elastic fibers appear in the muscular wall after puberty.
Congenital Anomalies
Abnormal development of the paratesticular region may result in a variety of anomalies, including embryonic remnants, agenesis, atresia, ectopia, and cysts. There is an increased frequency of anomalies in boys with cryptorchidism and congenital rubella. Bilateral anomalies result in sterility.
Agenesis and atresia of the testis, epididymis, and vas deferens result from failure of development of the genital ridge, often with anomalies of other wolffian derivatives and renal ectopia, agenesis, or dysplasia. Congenital absence of the vas deferens may be autosomal recessive, partial or complete, unilateral or bilateral, and is often associated with cystic fibrosis (see later). Testicular biopsies in patients with congenital absence of the vas deferens reveal normal spermatogenesis or hypospermatogenesis in up to 45% of cases, and clinical investigation should include semen analysis, renal ultrasound, and genetic cystic fibrosis screening. Congenital unilateral absence of the vas deferens is more commonly associated with renal agenesis than bilateral absence (74% versus 12%, respectively).
Duplications may involve any structure of the adnexa, but they are rare. Ectopic insertion of the ureteric bud in the epididymis, vas deferens, or seminal vesicles also may occur. Congenital or developmental cysts of the epididymis are rare and may be associated with intrauterine exposure to diethylstilbestrol. The cysts are usually solitary but may be multiple and bilateral. Ectopic epididymis may be found anterior to the testis, in the retroperitoneum, and within the kidney. Epididymal abnormalities are commonly associated with ectopic or cryptorchid testes (72% of cases), ranging from simple elongation of the epididymis (33%) to more complex changes such as complete disruption (39%).
Splenogonadal Fusion
Splenogonadal fusion is a rare congenital anomaly in which there is fusion of the splenic and gonadal anlage. About 100 cases have been reported, usually on the left side (98%) in men (95%). Patients may present with nontender scrotal mass or intestinal obstruction, but most cases are discovered incidentally at autopsy or surgery for cryptorchidism or inguinal hernia. About 57% are associated with other congenital anomalies, including peromelia, micrognathia, and cardiac anomalies. Hepatogonadal fusion has also been reported.
There are two types of splenogonadal fusion. The continuous type is characterized by connection of the spleen and the splenogonad by a fibrous cord. The cord usually arises in the upper pole of the spleen and may be retroperitoneal or anterior to the small bowel or colon. Splenic tissue may be present at both ends of the cord or stud the cord throughout its length. The discontinuous type of splenogonadal fusion has no connection between the spleen and splenogonad. The splenic tissue appears within the tunica albuginea or scrotum, or along the vascular pedicle.
Splenogonadal fusion probably results from early fusion of the spleen and gonad during embryonic development, perhaps as the result of inflammation or adhesions. The spleen develops during the fourth and fifth weeks of gestation, and rotates into proximity with the urogenital fold and developing gonadal mesoderm. During the eighth to tenth weeks, the gonads migrate caudally, probably accompanied by a portion of the spleen in cases of splenogonadal fusion. The limb buds and mandible are developing at the same time, accounting for the close association of splenogonadal fusion with peromelia and micrognathia.
Preoperative diagnosis of splenogonadal fusion by splenic scan may avoid unnecessary orchiectomy. Splenogonadal fusion and accessory spleen are important to consider when splenic ablation is needed.
Adrenal Heterotopia and Renal Ectopia
Adrenal cortical tissue may be present anywhere along the route of descent of the testis from the abdomen to the scrotum. It is usually an incidental finding at inguinal herniorrhaphy or epididymoorchiectomy, present in 1% to 3% of children undergoing such operations. Adrenal cortical tissue has been identified in inguinal hernia sac, spermatic cord ( Fig. 14.2 ), epididymis, and rete testis. It may present as a palpable tumor, and appears as small, round-to-oval, 1 to 5 mm in diameter, yellow-orange nodules, usually near the inguinal ring. The lesions almost always consist of adrenal cortical tissue resembling zona glomerulosa and fasciculata. Rarely they contain medullary tissue. Involution during childhood is the rule, but exceptional cases persist and become functional, rarely harboring neoplasms or developing into “tumors” in the adrenogenital syndrome and Nelson syndrome; rare cases occur in adults. Removal of functional rests may result in adrenal insufficiency. Ectopic renal tissue has rarely been observed in the scrotum, consisting of tubules and immature glomeruli.
Wolffian and Müllerian Remnants
Numerous embryonic remnants are found in the paratesticular area, including the appendix testis (hydatid of Morgagni), appendix epididymis, paradidymis, and vasa aberrantia. Precise classification of cystic remnants may be challenging.
Appendix Testis (Hydatid of Morgagni)
The appendix testis is attached to the surface of more than 90% of testes at autopsy; ultrasound examination found an incidence rate of 44%. This structure is located at the superior pole of the testis adjacent to the epididymis. Grossly it varies from 2 to 4 mm, appearing as a polypoid or sessile nodular excrescence. Microscopically it consists of a fibrovascular core of loose connective tissue covered by simple cuboidal or low columnar müllerian-type epithelium that is in continuity with the tunica vaginalis at the base. The fibrovascular core may contain tubular inclusions lined by similar cuboidal epithelium. Torsion of the appendix testis may be painful and mimic testicular torsion, and is the most common cause of acute scrotum in children.
The severity of the acute inflammatory cell infiltrates is associated with longer duration of symptoms and clinical evidence of torsion of the testicular appendages. No other association was detected between the pattern or degree of acute inflammatory cell infiltrate and any other clinicopathologic variable that may indicate pyogenic infection. No bacteria or fungal elements were identified. Marked lymphatic dilation may be the only histologic finding to indicate the presence of early torsion in cases of scrotal pain secondary to torsion of the appendix testis.
Appendix Epididymis (Vestigial Caudal Mesonephric Collecting Tubule)
The appendix epididymis is present in about 35% of testicles examined at autopsy; ultrasound examination found an incidence rate of 18%. Grossly it is a pedunculated spherical cystic or elongate structure arising from the anterosuperior pole of the head of the epididymis. Microscopically it is lined by cuboidal to low columnar epithelium that may be ciliated and show secretory activity. The wall consists of loose connective tissue and is covered by flattened mesothelial cells that are continuous with the visceral tunica vaginalis. The appendix epididymis may become dilated by serous fluid and, when enlarged, may mimic a tumor. Torsion may occur, sometimes in cryptorchidism.
Paradidymis (Organ of Giraldes)
This wolffian duct embryonic remnant consists of clusters of tubules lined by cuboidal to low columnar epithelium within the connective tissue of the spermatic cord, superior to the head of the epididymis.
Vasa Aberrantia (Organ of Haller)
Vasa aberrantia are wolffian duct remnants that appear as clusters of tubules that are histologically similar to the paradidymis. They arise within the groove between the testis and epididymis. Torsion of the vas aberrans is rare.
Other Lesions Associated With the Epididymis
Other rare epididymal lesions have been described, including epididymal cyst, duplication, and ectopic epididymal tissue associated with inguinal hernia. Cyst and duplication may arise from the caudal vasa aberrantia.
Walthard Rest
The remnant Walthard rest, probably of müllerian origin, consists of solid and cystic nests of uniform epithelial cells with ovoid nuclei and characteristic longitudinal grooves.
Hernia Sac Specimens: Glandular Inclusions Versus Vas Deferens or Epididymis
Herniorrhaphy in children is surgically challenging, particularly in strangulated hernia sac, accounting for the vulnerability of the epididymis and vas deferens that may be inadvertently transected during the procedure. This problem is compounded by the diagnostic difficulty in classifying glandular inclusions in hernia sacs; a challenging problem in young children is separating these structures and embryonic remnants before puberty. Benign glandular inclusions in inguinal herniorrhaphy specimens may represent Müllerian remnants, wolffian remnants, transected vas deferens, or transected epididymis. It is critical to make this distinction due to the potential impact on reproductive function and medicolegal issues. Disruption of one vas deferens may generate antisperm antibodies.
Classification of glandular inclusions is often subjective; in one study, interobserver agreement was reported in only 44% to 52% of cases. Epididymis typically has a well-formed concentric muscular coat, whereas embryonic remnants lack a muscular coat but have a mantle of fibrous tissue. Some have advocated the use of Masson trichrome stain and muscle-specific actin to make this distinction, but this has been refuted by others as inconclusive. Comparative analysis reveals that the combination of glandular diameter (with special attention to patient age, recognizing possible changes with advancing development) and histochemical and immunohistochemical stains (trichrome, muscle-specific actin, and CD10) should allow distinction in most cases ( Table 14.2 ). Reliance on light microscopic features alone may be misleading.
Table 14.2
Glandular Inclusions in Herniorrhaphies: Comparative Features
| Incidence in Herniorrhaphies (%) | Mean Diameter (mm) | Immunophenotype | |
|---|---|---|---|
| Embryonic remnants | 1.5 | 0.17 | Muscle-specific actin negative; CD10 negative -38 |
| 2.6 | 0.20 | ||
| 2.9 | |||
| 6.0 | |||
| Vas deferens | 0.16 | 0.6 | Muscle-specific actin positive in wall; CD10 positive + 38 |
| 0.23 | 1.2-1.4 (age, 4 months) | ||
| Epididymis | 0.16 | 0.20 | Muscle-specific actin positive in wall; CD10 positive + in epithelium |
| 0.30 | |||
| 0.88 |
Should inguinal hernia repair specimens be routinely submitted for histopathologic examination? One study of 456 specimens from 371 patients younger than 20 years revealed four unexpected cases with epididymal tissue (1%), leading the authors to conclude that pathologic study was an unnecessary expense. In a study of almost 1500 inguinal herniorrhaphies, the authors found vas deferens in 0.13% of cases ( Table 14.2 ). Another report of more than 7000 consecutive pediatric herniorrhaphies found incidence rates of 0.23% vas deferens, 0.3% epididymis, and 0.41% embryonal rests. Inguinal hernia characteristically shows cremasteric muscle fiber hypertrophy that accounts for the palpable thickening of the spermatic cord (see later Hamartoma [Smooth Muscle Hyperplasia] section).
Cystic Fibrosis
Cystic fibrosis is a genetic abnormality that often affects the testicular adnexa, resulting in infertility due to agenesis or atresia of mesonephric structures or anomalies of the testes (see Chapter 12 ). Patients with congenital bilateral absence of vas deferens often have cystic fibrosis, although this finding may occur in patients without cystic fibrosis.
Nonneoplastic Diseases of the Spermatic Cord and Testicular Adnexa
“Celes” and Cysts
Hydrocele
This mesothelial-lined cyst results from accumulation of serous fluid between the parietal and visceral tunica vaginalis of the testis ( Fig. 14.3 ). There are two variations of spermatic cord hydrocele: the “encysted” variety that does not communicate with the peritoneal cavity, caused by defective closure at both proximal and distal ends of processus vaginalis; and the “funicular” variety that does communicate with the peritoneal cavity, caused by defective closure of only the distal end of tunica vaginalis. The encysted type can be confused with an inguinal mass (lymphadenopathy, hernia) and a primary tumor of the cord.
Congenital hydrocele occurs when a patent processus vaginalis within the spermatic cord communicates with the peritoneal cavity. The prevalence of congenital hydrocele is about 6% at birth and 1% in adulthood. Most cases of hydrocele are idiopathic, but they may be associated with inguinal hernia, scrotal trauma, epididymoorchitis, or tumors of the testis or paratesticular region. Possible causes of idiopathic hydrocele include excessive secretion within the testicular tunics by parietal mesothelial cells, decreased reabsorption, and congenital absence of efferent lymphatics.
Hydrocele is lined by a single layer of cuboidal or flattened mesothelial cells, sometimes with prominent atypia, with underlying connective tissue stroma. The luminal fluid is usually clear and serous unless complicated by infection or hemorrhage. The surface is often covered by fibrinous adhesions and inflammation, and subepithelial chronic inflammation and fibrosis may be present. In some cases progressive fibrosis narrows or obliterates the cyst lumen, creating adhesions and multiple cysts. Spermatocele may rupture into the hydrocele sac.
Contralateral hydrocele, commonly seen in cases of neonatal testicular torsion, is of minimal clinical significance and does not warrant formal inguinal exploration for treatment, thereby minimizing the potential of contralateral spermatic cord injury in the neonate.
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