TFE3 and renal cell carcinoma: Recently, break-apart fluorescence in situ hybridization (FISH) assay in FFPE archival sections is viewed as the optimal test for diagnosing Xp11.2 RCC for most laboratories [23] (However, the break-apart FISH assay is less useful than TFE3 immunohistochemistry in detecting some Xp11.2 RCCs, like the RBM10-TFE3 RCC which are associated with a subtle chromosome inversion [9]).