Cystic rete testis associated with cryptorchidism in a horse.

The research discusses a rare case of cyst formation in a horse’s testis accompanied by cryptorchidism. An extensive clinical examination, surgical procedures, and histopathological analysis were performed to investigate the causes and characteristics of the cyst, leading to a diagnosis of cystic rete testis.

Case Presentation

• The study describes a case with a 2-year-old Clydesdale stallion with cryptorchidism, a condition where one or both of the testes fail to descend.
• The horse was admitted for castration due to the non-palpable left testis in the inguinal canal, which was inaccessible despite exploration and enlargement surgical efforts.
• The atypical situation led to an in-depth investigation using anesthesia and surgical procedures trying to locate and understand the state of the left testis.
• Post-procedure, an abdominal testis, round and approximately 20 cm in diameter, was observed filled with fluid. The testis was removed after fluid aspiration.

Pathological Findings

• The removed testis was found atrophic with a large cyst that protruded from its dorsal surface. The cyst, measuring 16x16x10 cm, was filled with dark yellow fluid.
• The cyst’s wall was firmly attached to the tunica albuginea, the protective layer of the testis, and had a gray to pearlescent smooth lining.
• Upon further microscopic examination of the cyst wall, findings indicated a single layer of low cuboidal epithelial cells organized on a thin collagen-poor propria overlaying a hypocellular fibrous stroma.
• Evidence of atrophic seminiferous tubules trapped between the fibrous lining of the cyst wall and the tunica albuginea was also presented.

Final Diagnosis

• The investigation concluding with a diagnosis of cystic rete testis based on several criteria.
• First, the intratesticular location of the cyst is confirmed through the presence of trapped atrophic seminiferous tubules between the cyst wall and the tunica albuginea.
• Second, the lining of the cyst included simple low cuboidal epithelium arranged on a non-collagenous propria and a layer of dense collagenous connective tissue.
• Third, the absence of teratomatous tissue within the testis, and fourth, no subepithelial smooth myofibers were observed as typical for cysts of the epididymis of the appendix.

Scientific Insights and Comparative Discussion

• The report mentions previous studies that noted cysts in testes of domestic animals, like the cystic rete testis, cysts of the appendix epididymis, and hydrocele.
• While it is suggested that cysts can prevent the descent of an embryonic testis, instances of cysts in equine testis have been closely associated with teratomas and cryptorchidism.
• The report argues that the rare occurrence of cystic rete testis could be due to the inherent structure of the rete testis, embedded in a fibrous mediastinum, which ordinarily prevents dilation.