Immunocytochemical p63 expression discriminates between primary cutaneous follicle centre cell and diffuse large B cell lymphoma-leg type, and is of the TAp63 isoform.

Aims: The p63 gene shares structural and functional homologies with the p53 family of transcriptional activators, but differs in exhibiting a consistent expression pattern in normal tissues. Although p63 is rarely mutated in malignancy studies of primary human tumours and cell lines suggest that p63 may promote tumour development. In non-Hodgkin's nodal lymphoma, TAp63 expression in follicular lymphoma (54%) and diffuse large B cell lymphoma (34%) has been described and correlated with the proliferative index. In this study, we analysed a series of primary cutaneous B cell lymphomas for immunohistochemical expression of p63.

Methods And Results: Thirty cases of diffuse large B cell lymphoma leg type (pcDLBCLL) and 34 cases of follicle centre cell lymphoma (pcFCCL) were stained using a generic antibody to p63, and a subset of these with an antibody specific for delta-Np63 isoform. The results indicate a significant difference between pcDLBCLL (21 of 30) and pcFCCL (four of 34) in p63 expression (P = 0.000); expression correlated strongly with the proliferation rate as assessed by Ki-67 (P = 0.015). None of the p63((+)) cases tested expressed the delta-Np63 isoform, suggesting that expression is of the TAp63 isoform.

Conclusions: Functional studies are required to clarify the significance of p63 overexpression in primary cutaneous B cell lymphoma.