The WT1 gene was identified as a tumor suppressor gene located at 11p13 and is involved in the development of Wilm’s tumor. Ever since WT1 has been identified as a molecular target for cancer immunotherapy, immunohistochemical detection of WT1 protein in tumor cells has become an essential part of routine practice. WT1-positive tumors includes tumors of the stomach, prostate, biliary and urinary systems and malignant melanomas. However, in recent studies it was found out that WT1 protein plays an oncogenic role rather than tumor-suppressive role in human cancers.