TFE3 and neoplasm: TFE3 gene mutation study was further done at John Hopkins Hospital, Baltimore, where immunostains showed tumor cells to be positive for TFE3 but negative for cathepsin K. FISH analysis showed 55% and 36.7% cells to have split TFE3 signal in patient 1 and patient 2, respectively, supporting a diagnosis of translocation renal cell carcinoma.