Diagnostic value of p53 protein in the study of serous effusions.

The differential diagnosis between neoplastic and reactive mesothelial cells is one of the most frequent problems in the study of serous effusions. We assessed the utility of the immunohistochemical determination of p53 protein as a marker of malignancy in 34 embedded blocks of neoplastic fluids and 30 nonneoplastic effusions. Eleven (32.4%) of the tumor fluids were positive for this antibody, while all the nonneoplastic fluids were negative. A specificity of 100% and a sensitivity of 59% were observed. The immunohistochemical determination of p53 protein seems to be helpful in the differential diagnosis of effusions; its principal limitation is its relatively low sensitivity.