To improve the accuracy of diagnosis of Xp11.2 tRCC and ASPL-TFE3 renal cell carcinoma (RCC), we investigated newly designed fluorescence in situ hybridization (FISH) probes (diagnostic accuracy study). The gene discussed is TFE3; the disease is renal cell carcinoma associated with Xp11.2 translocations/TFE3 gene fusions.