Expression of p63 in reactive hyperplasias and malignant lymphomas.

p63 is a recently described p53 homologue. It is involved in survival and differentiation of reserve/stem cells in epithelia. To obtain new insights into the role of p63 in malignant lymphomas (MLs), immunohistochemical staining for p63 and p53 was performed in 126 cases of MLs. p63 was expressed in 38 cases of MLs (30.2%) including 32/61 cases (52.5%) of diffuse large B-cell lymphoma (DLBCL), 1/8 cases (12.5%) of precursor T-lymphoblastic lymphoma (T-LBL), 4/14 cases (28.6%) of follicular lymphoma, 1/6 cases (16.7%) of T/NK cell lymphoma. Among p63 positive cases, p63 was strongly expressed in 15/32 cases of DLBCL and 1/1 case of T-LBL. p63 was not expressed in mantle cell lymphomas, peripheral T-cell lymphomas, marginal zone B-cell lymphomas, plasma cell myelomas and Hodgkin's lymphomas. p63 was coexpressed with p53 in 18/38 p63 positive cases in which only 4 cases were strongly coexpressed. All p63+/p53+ cases were DLBCL. p63 overexpression (above 30%) cases showed significant poor survival (p=0.0228) in DLBCL. However, there was no statistically significant correlation between p63 expression and IPI score on Multivariate analysis. We could speculate that p63 could act indirectly as an oncogene by inhibiting p53 functions. Stage of differentiation of neoplastic lymphocytes appears to have a correlation with p63 expression in MLs.