Expression of p21 is dependent on or independent of p53 in carcinoma ex pleomorphic adenoma (undifferentiated and adenocarcinoma types).

Our study is aimed to characterize alteration in the immunohistochemical expression of p21 and p53 in normal tissue of the salivary gland surrounding carcinoma arising in pleomorphic adenoma, and the tumor cells of carcinoma arising in pleomorphic adenoma as well as to identify whether the induction of expression p21 is dependent on or independent of p53 in carcinoma arising in pleomorphic adenoma. A selected series of 27 cases of carcinoma ex pleomorphic adenoma (undifferentiated and adenocarcinoma types) was examined. The results showed that p21 and p53 expression was negative in the most components of normal tissue of the salivary gland surrounding carcinoma arising in pleomorphic adenoma. p21 was strongly expressed in carcinoma cells in 9 (33.3%) cases out of 27. p53 was strongly expressed in carcinoma cells in 10 (37%) cases out of 27. Also a co-expression of p21 and p53 showed negative nuclear staining in 9 cases, while 8 cases expressed positive staining. p21 expressed negative nuclear staining in 4 cases but p53 expressed positive staining in the same cases. p21 expressed positive nuclear staining in 6 cases but p53 expressed negative nuclear staining in the same cases. Our data suggest that inactivation of p53 and p21 may play an important role in the evolution of carcinoma ex pleomorphic adenoma. Also p21 behaves as dependent on or independent of p53 in carcinoma arising in pleomorphic adenoma.