For example, in Martignoni et al’s study [22], 8 ASPL-TFE3 RCCs entirely did not express cathepsin K. Nevertheless, 12 of 14 PRCC-TFE3 RCCs and all 18 alveolar soft part sarcomas were positive for this protein. The gene discussed is CTSK; the disease is alveolar soft part sarcoma.