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

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.