Original contributionImmunophenotypic comparison of testicular sclerosing Sertoli cell tumors and Sertoli cell tumors not otherwise specified

- Testicular Sertoli cell tumors (SCTs) are rare, and most are benign.
- Most SCTs are classified as not otherwise specified (SCT-NOS).
- Sclerosing SCT (S-SCT) is now considered a variant of SCT-NOS.
- Immunophenotypic differences between SCT-NOS and SCT-NOS were reported.
- S-SCT and SCT-NOS differ only in the amount of fibrosis and expression of PAX2/PAX8.

SummaryTesticular Sertoli cell tumors (SCTs) are rare, and most fall into the category of SCT-not otherwise specified (SCT-NOS). Only a few additional types of SCT are recognized. Sclerosing SCT (S-SCT), originally described in 1991, comprises a small fraction of SCTs and was considered a specific entity until the 2016 revision of the World Health Organization classification of non-germ cell tumors, where it was classified as a morphologic variant of SCT-NOS. In a recent study, differences in expression of PAX2/PAX8, inhibin, androgen receptor, and S100 protein between SCT-NOS and S-SCT were noted in a small number of cases. In this interinstitutional study, we compared the expression of these markers and β-catenin in 11 cases each of SCT-NOS and S-SCT to determine if differences exist that could justify keeping a separate classification of these neoplasms. PAX2/PAX8 cocktail was the only marker that was significantly overexpressed in S-SCT. Expression of androgen receptors was strong in S-SCT and variable in SCT-NOS but did not reach statistical significance. Expression of β-catenin was common in both, whereas inhibin was infrequent. The available material was insufficient for a conclusive evaluation of S100 protein expression. Overall, our results support the inclusion of S-SCT as a morphologic variant of SCT-NOS. Expression of PAX2/PAX8 in S-SCT may reflect an overactive epithelial-to-mesenchymal transition as has been shown in experimental models of acute and chronic seminiferous tubular injury and might be related to the process generating the stroma in these tumors.