Mesothelioma of tunica vaginalis of "uncertain malignant potential" - an evolving concept: case report and review of the literature

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/3445715895747607 webcite.Mesothelioma of tunica vaginalis is a rare neoplasm comprising less than 1% of all mesotheliomas, with over 200 cases documented in the literature [1]. Diffuse malignant mesotheliomas of tunica vaginalis are highly aggressive tumors with rapid progression, resulting in local recurrence, regional and distant metastases and death. Over the years, a category of rare well-differentiated papillary mesotheliomas (WDPM) has emerged, which demonstrated indolent behavior, in stark contrast to diffuse malignant mesotheliomas. These neoplasms were reminiscent of the bland mesothelial tumors with similar morphology, which were first described in the peritoneal cavity of younger females [2]. Similar tumors were also described in the pleura, peritoneum and pericardium, and also in male patients [3,4]. By definition, WDPM of tunica vaginalis do not exhibit stromal invasion, which sometimes can be difficult to evaluate on microscopic examination [5]. It has been proposed recently that the designation WDPM be restricted only to WDPM of tunica vaginalis lacking any complex or adverse pathology, while the cases with more complex morphology that do not show overt signs of malignancy should be designated "mesothelioma of uncertain malignant potential" [6].We present a case which highlights the difficulty of clearly categorizing a case either as WDPM or malignant mesothelioma, which reiterates the need of introducing a diagnostic category of mesothelioma of tunica vaginalis of "uncertain malignant potential". Currently, there are no specific treatment recommendations for WDPM or mesotheliomas of "uncertain malignant potential" and it is important that these uncommon tumors are well characterized and their long-term behavior documented, which will enable establishing evidence-based treatment guidelines.A 57-year-old patient presented with asymptomatic hydrocele f