Objective: Our study aimed to characterize alteration in the immunohistochemical expression of p21 in normal tissue of the salivary gland surrounding pleomorphic adenoma, the tumor cells of pleomorphic adenomas, and carcinoma arising in pleomorphic adenoma. Study design: A selected series of 29 cases of pleomorphic adenomas, and 27 cases of carcinoma ex-pleomorphic adenoma (undifferentiated and adenocarcinoma types) were examined. Results: The results showed that p21 expression was negative in the most components of normal tissue of the salivary gland surrounding pleomorphic adenoma, 24 cases out of 29 of the non tumour duct cells (82.8%), and 28 (96.6%) cases out of 29 of the acinar cells shows negative p21 expression. P21 expression in pleomorphic adenomas shows that 2 cases out of 29 (6.9%) strongly expressed in the duct cells. p21 was strongly expressed in carcinoma cells in 9 (33.3%) cases out of 27. Conclusion: Our data suggest that the strong nuclear staining as an indicator for altered p21, then the alteration of p21 expression would increase from pleomorphic adenoma to carcinoma arising in pleomorphic adenomas (6.9% versus 33.3%).