TMPRSS2::ETS translocation in nonprostatic malignancies: an unexpected finding in thymic carcinoma and pulmonary adenocarcinoma

TMPRSS2::ETS fusions occur in about half of the prostate adenocarcinomas and are generally considered characteristic and even diagnostic of this tumour. Despite this fact, the frequency of this fusion is not well established in other tumour types. Incidental identification of a TMPRSS2::ETV1 fusion in a thymic squamous cell carcinoma prompted us to assess 1758 solid tumours by next-generation sequencing panel for TMPRSS2::ETS fusions, including 1690 non-prostatic malignancies. In addition to 28 of the 68 prostatic adenocarcinomas, we identified TMPRRS2::ETS fusion in two non-prostatic tumours, where a prostatic adenocarcinoma could be confidently excluded. Besides the TMPRSS2::ETV1 fusion identified in the thymic carcinoma, we also observed TMPRSS2::ERG fusion in pulmonary adenocarcinoma. Both patients were male, which would support an androgen-driven background. Our findings suggest that although at a low frequency, TMPRSS2::ETS fusion may occur in non-prostatic tumours, and sole reliance on its identification can potentially result in erroneous diagnostic conclusions.