Analysis of benign neoplasms of the rete testis formerly termed "Sertoliform cystadenomas" demonstrates that they are not Sertoli cell tumours with intra-rete growth

Abstract

Aims: Benign tumours of the rete testis include mostly cystadenomas and adenomas. A subset with tubular or tubulopapillary architecture shows morphological similarities to Sertoli cell tumours; these neoplasms were previously termed "Sertoliform cystadenomas of the rete testis". In the most recent WHO classification, they have been interpreted as Sertoli cell tumours, not otherwise specified (NOS), with pure intra-rete growth, and therefore excluded as an entity. The remaining cystadenomas of the rete testis vaguely resemble tumours of Mullerian origin arising in the ovaries. In this study we analyse benign tumours of the rete testis, including a subset with Sertoliform features.

Methods and results: Benign neoplasms of the rete testis were identified through query of consultation and institutional files. Clinicopathologic data were collected, and available slides were reviewed. Cases were assessed using IHC and three separate DNA sequencing panels. Eleven tumours from patients 32-78 years old were evaluated. Four were classified as Sertoliform adenomas/cystadenomas, displaying tubulo-papillary or tubular/trabecular architecture; all of them were PAX8-positive and lacked nuclear beta-catenin expression. The remaining seven tumours were benign cystadenomas NOS. Genomic analysis was performed successfully in 10/11 tumours (including all Sertoliform adenomas/cystadenomas) and revealed no pathogenic variants in CTNNB1, KRAS, or BRAF.

Conclusion: Sertoliform cystadenomas of the rete testis differ from Sertoli cell tumours NOS, as evidenced by the absence of molecular markers characteristic of Sertoli cell tumours. The remaining benign cystadenomas lack molecular alterations seen in Mullerian tumors of the ovaries.

Keywords: Sertoliform cystadenoma; adenomatous hyperplasia rete; orchiectomy; paratestis; rete testis; testicular neoplasm.

Figure 1

“Sertoliform” adenoma/cystadenoma of the rete testis. A,B: The tumours displayed elongated, branching tubules, often continuous with slender papillary structures that occasionally branched. C: Fibrovascular cores showed marked hyalinization, suggestive of abundant basement membrane material from one tumour. D,E: Solid areas displaying tubular and trabecular growth patterns. The trabeculae exhibited a parallel arrangement of epithelial cells, reminiscent of a “train track” in certain regions, along with a prominent intratumoral lymphocytic infiltrate. Some tubules contained hyaline globules. [Color figure can be viewed at wileyonlinelibrary.com]

Figure 2

“Sertoliform” adenoma/cystadenoma of the rete testis. A–C: Transition areas between the flat, nonneoplastic epithelium of the rete and the neoplastic epithelium. [Color figure can be viewed at wileyonlinelibrary.com]

Figure 3

“Sertoliform” adenoma/cystadenoma of the rete testis. A: PAX8 showed diffuse nuclear expression. B: Beta catenin expression restricted to the cytoplasmic membrane. [Color figure can be viewed at wileyonlinelibrary.com]

Figure 4

Cystadenoma of the rete testis. A: Mucinous subtype. B: Seromucinous subtype, lined by cuboidal to columnar epithelial cells, including a population of ciliated cells (fallopian tube‐like epithelium). [Color figure can be viewed at wileyonlinelibrary.com]

Figure 5

Cystadenoma of the rete testis. A,B: Serous subtype, characterized by unilocular structure with no internal septations, lined by a single layer of epithelial cells. B: One serous neoplasm exhibited focal epithelial proliferation with stubby, branching papillae. The epithelium lining the papillae exhibited mild nuclear atypia, featuring conspicuous nucleoli. [Color figure can be viewed at wileyonlinelibrary.com]

Figure 6

Cystadenoma of the rete testis. Focal areas with ovarian‐like stroma. [Color figure can be viewed at wileyonlinelibrary.com]

Figure 7

Hyperplasia of the extratesticular portion of the rete testis. A: The rete testis consists of three parts: the septal rete testis containing tubuli recti (right towards the testicular parenchyma), the hilar/mediastinal rete testis containing wide anastomosing channels lined by flat epithelium (centre), and the extratesticular rete testis containing efferent ducts (left, towards the epididymis). B: This case shows hyperplasia of efferent ducts confined to the extratesticular portion of the rete testis. We hypothesize that lesions arising in different portions of the rete may show phenotypic differences, which could explain the variable immunoprofile reported in adenomas of the rete testis. [Color figure can be viewed at wileyonlinelibrary.com]