The aims of the present study were (a) to evaluate the utility of TFE3 break-apart FISH in establishing the diagnosis of Xp11.2 RCC in cases with suspicious pathological features and to assess the accuracy of TFE3 immunostaining by comparing with the FISH assay; and (b) to delineate further the incidence, clinicopathological features, and clinical outcomes of adult Xp11.2 RCC by comparing with non-Xp11.2 RCC patients. This evidence concerns the gene TFE3 and renal cell carcinoma.