non-neoplastic rete epithelial proliferations

Adenomatous rete testis hyperplasia

Real or apparent adenomatous hyperplasia of the rete occurs in association with various testicular abnormalities, most frequently testicular atrophy.

In these cases, the appearance is probably one of relative prominence rather than a ’true’ hyperplasia, but the distinction between hyperplasia and relative prominence is arbitrary.

Bona fide hyperplasia is usually an incidental finding and is grossly manifest as a solid or cystic mass in less than half of the cases.

In these cases, the separation between hyperplasia and adenoma is also debatable but again of no clinical importance.

Microscopically, adenomatous hyperplasia is characterized by a complex interconnecting proliferation of tubulopapillary channels that may be focal or diffuse and with or without cystic dilatation.

The lumens may be empty, sperm containing or have eosinophilic secretion. The lining cells are cuboidal to low columnar with innocuous cytology.

Continuity with nonhyperplastic rete provides clues to a rete origin and the incidental presentation and usual background of other testicular pathology indicates a non-neoplastic nature.

Adenomatous rete testis hyperplasia has been reported in patients with cryptorchidism, various nongerm cell tumors and in patients with chronic hepatic insufficiency and bilateral renal dysplasia.

In patients with germ cell tumors, another form of hyperplasia occurs which, in contrast to ’adenomatous hyperplasia,’ is invariably an incidental finding and is not grossly cystic.

In these cases, hyperplastic rete epithelium fills variably expanded channels often with intracytoplasmic eosinophilic (less than 1 mum to greater than 10 mum) hyaline globules.

This pattern may be mistaken for yolk sac tumor, although the arborizing architecture of the rete is retained and is diagnostic of the process.

The globules most likely represent proteins absorbed by hyperplastic rete epithelium, which is stimulated by neoplastic invasion.

References

 Jones EC, Murray SK, Young RH. Cysts and epithelial proliferations of the testicular collecting system (including rete testis) Seminars in Diagnostic Pathology. 2000;17(4):270–293. [PubMed]

 Amin MB. Selected other problematic testicular and paratesticular lesions: rete testis neoplasms and pseudotumors, mesothelial lesions and secondary tumors. Modern Pathology. 2005;18(supplement 2):S131–S145. [15502808]