Well-differentiated papillary mesothelial tumour (WDPMT), classically presenting in the peritoneum of young female patients, is exceedingly rare in the tunica vaginalis, with less than 20 cases reported in the literature. 1-3 While WDPMT are thought to be indolent in nature, there is a paucity of long-term follow-up studies, and tumorigenesis is not fully elucidated. 1-3 Here, we discuss a case of a WDPMT of the tunica vaginalis in a male in the second decade of life, presenting as an exophytic lesion found at time of hydrocele drainage. Histology of tunical mesothelium demonstrated papillary projections lined by bland cuboidal to columnar cells, with no atypia or invasion. The tumour cells showed positive immunohistochemical staining for mesothelial markers, calretinin and WT1, and negative epithelial markers. This case demonstrates the diagnostic challenges of recognising WDPMT, a rare entity in the tunica vaginalis, and the pertinence of an appropriate immunohistochemistry panel to distinguish it from important differential diagnoses such as serous borderline tumour.
Zafir et al. (Sun,) studied this question.