[Mesotheliomas of the tunica vaginalis testis]

Three observations of mesotheliomas of the vaginal sheath of the testis are described. In two cases the histological structure of the tumour corresponded to papillar mesothelioma, in one to fibromesothelioma. Direct transitions of the normal mesothelial lining of the testis sheaths through intermediate stages to typical tumour structures were discovered permitting to refute the disontogenetic nature of mesotheliomas of the testis.