Cathepsin K immunoexpression is non-specific and has been reported in renal cell tumors, granular cell tumors, as well as numerous additional sarcomas including Kaposi sarcoma, liposarcoma, chondrosarcoma, undifferentiated pleomorphic sarcoma, and leiomyosarcoma (21). The gene discussed is CTSK; the disease is undifferentiated pleomorphic sarcoma.