Mona M Abdo¹⁾, Nadia A Elsissy²⁾, Naglaa  M Abdelrazek³⁾,Reham M Nagieb^{4) 1)}: Teaching assistant (2015), Department of Oral Pathology, Faculty of Dentistry, Mansoura University ²⁾:Professor of Oral Pathology Department ,Faculty of Dentistry , Mansoura University                                                              ³⁾:Associate Professor of Oral Pathology, Faculty of Dentistry ,Mansoura University ⁴⁾:Assistant Professor of pathology ,Faculty of Medicine ,Mansoura University Abstract: Introduction: Pleomorphic adenoma (PA) is the most common salivary gland tumor in which 6.2% of cases transform into malignancy , most commonly ;to carcinoma ex plemorphic adenoma (CXPA). Consequently, it is necessary to determine sensitive diagnostic biomarkers, and markers, for accurate diagnosis and proper treatment planning                                                                                                 Aim: This study was conducted to examine the cellular distribution of WT1 its clinical significance in differential diagnosis of PA and CXPA . Methods: The expression levels of WT1 in tumor cells was determined immunohistochemically in 19 cases of PA and 8 cases  of CXPA and correlations between WT1 expression and clinicopathological parameters were analyzed. Results: Statistical analysis in comparison between PA and CXPA revealed significant difference in WT1 expression, intensity and cellular localization. No statistical significant difference was found of clinical data in expression of WT1.      Conclusion: These results suggest that WT1 may play an important role in the process of carcinogenesis and can be a strong predictor of malignant transformation in PA.