Molecular Characterization of Testicular Mesothelioma and the Role of Asbestos as a Causative Factor

center dot Context.-Mesothelioma of the tunica vaginalis testis (TVT) is an extremely rare form of mesothelioma. Objective.-To compare the clinical and molecular characteristics of mesothelioma of the TVT with those of mesothelioma at other more common sites, including the relationship with exposure to asbestos. Design.-We present clinical and pathological data for 9 cases of primary TVT mesothelioma. We performed wholegenome sequencing on 3 cases for the first time. Results.-The majority (7 of 9 cases) of TVT mesotheliomas were epithelioid, with the remaining 2 cases showing biphasic morphology. Morphology and immuno histochemical profiles were indistinguishable from meso-thelioma elsewhere. Asbestos exposure was documented for 7 of the 9 cases, with no information for 2 cases. The 3 TVT mesothelioma cases that underwent whole-genome sequencing displayed a mutational profile similar to that of mesothelioma at other sites, including NF2 and TP53 mutations. Conclusions.-The clinical and molecular profile of TVT mesothelioma is similar to that of mesothelioma else-where.