p53 and PCNA coexpression of 81 pleural and peritoneal effusion specimens: an immunohistochemical study

Several studies have indicated that wild type p53 plays an important role in controlling cell growth and acts as a cyclin modifier. Abnormalities in p53 induce the overexpression of proliferating cell nuclear antigen. The aim of this study is to correlate immunocytochemically the expression of mutant p53 and the proliferative index (PI) as indicated by image analysis of PCNA immunoreactivity in 81 cases of pleural and peritoneal effusions. There was a strong correlation (r = 73%) between p53 immunoreactivity and PCNA PIs. Forty-three (71%) cases indicated p53 immunostaining out of 61 cases with PCNA immunoreactivity, forty of which (93%) proved to have a diagnosis of malignancy using histological or clinical data. Furthermore, 7 malignant cases showed PCNA reactivity but no p53 immunostaining. An additional four malignant cases indicated no reactivity for either p53 or PCNA. Also, there was a significant difference in the PCNA PI between benign and malignant effusions (p < 0.001). These clinical observations confirm the function of wild p53 as a check point during cell cycling, and as a strong negative feedback effect on PCNA expression. Furthermore, such co-expression represents a significant indicator for malignancy.