Beaumont M, Dugay F, Kammerer-Jacquet SF, et al. - Researchers evaluated the performance of fluorescence in situ hybridization (FISH) analysis in the histological classification of 359 renal cell carcinomas (RCC) showing unusual histological features and/or happening in young individuals. In 73% of the RCC (261/359), the FISH analysis added to the histological classification. Conversely, in 19% (69/359), FISH did not add to the diagnosis, and for the residual tumors, hybridization failure was noted (29/359). Given the various RCC subtypes, FISH analysis was found to be highly effective in authenticating the histological diagnosis of clear cell RCC, papillary RCC, and TFE3 translocation RCC, and was able to recognize abnormalities of the TFEB gene. Nevertheless, for the diagnosis of oncocytic tumors and unclassified RCC, this approach has some limitations, suggesting that extra molecular assays should be assessed in these cases.