WT1 and peripheral primitive neuroectodermal tumor: More recently, a study investigating the diagnostic utility of WT1 immunostaining in pediatric renal tumors used the 6F-H2 monoclonal antibody on 53 pediatric cases of renal tumors (38 nephroblastomas, 6 mesoblastic nephromas, 2 clear cell sarcomas, 2 ccRCCs, 2 peripheral neuroectodermal tumors, 1 AML, 1 rhabdomyosarcoma and 1 malignant rhabdoid tumor).