Well-differentiated Papillary Mesothelial Tumor of Tunica Vaginalis: A Case Report.

INTRODUCTION: Well-differentiated papillary mesothelial tumor (WDPMT) of the tunica vaginalis is an extremely rare entity that was recently reclassified by the World Health Organization. CASE PRESENTATION: We report a case of WDPMT in which intraoperative frozen section analysis suggested a malignant tumor, leading to radical orchiectomy. Postoperative histopathological examination demonstrated papillary mesothelial proliferation with retained BAP1 and MTAP expression, supporting the diagnosis of WDPMT. CONCLUSION: This case highlights the diagnostic challenges of WDPMT during surgery and the limitations of intraoperative frozen section analysis.