A 12-year-old boy presented with a cystic mass in the head of the right epididymis. At gross description, the lesion consists of an intact cyst measuring 3 cm in maximum diameter. On piercing the content is composed of clear fluid. No internal loculations or solid areas identified. Representative cross-sections were submitted.
Sections show part of the epididymis and a cyst with a thin fibrous wall lined by columnar ciliated epithelium without atypia or true stratification (Figures 1-2). In one area, a small tube-like structure with surrounding concentric smooth muscle is noted (Figure 3). Adjacent to this the epithelium lining the cyst is slightly more papillary in nature with infoldings (Figures 4).
The differential diagnosis considerations included:
Papillary cystadenoma of epididymis: Papillary cystadenoma of epididymis is a benign tumor that accounts for about 1/3 of all primary epididymal tumors. It appears as a cystic mass in the head of the epididymis and is bilateral in about 40%. It consists of dilated ducts lined by papillae with a single or a double layer of cuboidal to low columnar ciliated epithelium. About 2/3 of cases of papillary cystadenoma of the epididymis occur in patients with von Hippel-Lindau syndrome, and they are more frequently bilateral in this syndrome.
Simple epididymal cyst: Epididymal cysts are often very difficult to differentiate from spermatoceles, and definitive differentiation depends on aspiration of the cystic fluid. If sperm is present, the cystic mass is a spermatocele. If no sperm is present, the mass is probably an epididymal cyst.
Appendix epididymis (vestigial caudal mesonephric collecting tubule): The appendix epididymis 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 which may be ciliated and show secretory activity. The wall consists of loose connective tissue and is covered on its outer surface by flattened mesothelial cells that are continuous with the visceral tunica vaginalis. It may become dilated by serous fluid and mimic a tumor.
Paradidymis (organ of Giraldes): This wolfian 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 aberrans (organ of Haller): These wolfian ducts remnants appear as clusters of tubules that are histologically similar to the paradidymis. They arise within the groove between the testis and epididymis.
Hydrocele: A hydrocele is a collection of watery fluid around the testicle. This is a common problem in newborn males and usually goes away within the first year of life. When the testicle drops into the scrotum (about the eighth month of pregnancy), a sac (the processus vaginalis) from the abdominal cavity travels along with the testicle. Fluid can then flow to the scrotum to surround the testicle. This sac usually closes and the fluid is absorbed. Hydrocele is lined by a single layer of cuboidal or flattened mesothelial cells, sometimes with prominent atypia, with underlying connective tissue stroma.
Courtesy from Texas Pediatric Surgical Associates: www.pedisurg.com
Spermatocele: A spermatocele is a benign cystic accumulation of sperm often found in the head of the epididymis that usually presents as a smooth, firm, well-circumscribed mass along the testis. Spermatoceles are considered in the differential diagnosis of any scrotal mass and must be differentiated from hydroceles, varicoceles, epididymal cysts, and other scrotal masses.
Benign papillary mesothelioma: Benign papillary mesothelioma of the tunica vaginalis usually appears in young men and consists of a hydrocele sac with papillary excrescences and cystic and solid areas. Microscopically, there are complex papillae covered by cuboidal, columnar, or flattened mesothelial cells with large vesicular nuclei and glassy eosinophilic cytoplasm.
Papillary cystadenoma of epididymis.
Key Features:
