Use of p63/P504S monoclonal antibody cocktail in immunohistochemical staining of prostate tissue.

Diagnosis of prostate needle biopsies can be challenging, particularly when the atypical areas of interest are very small. The utility of immunostains for high-molecular-weight cytokeratin (34betaE12) to highlight prostatic basal cells in these cases is well established, and recent reports also document the utility of immunostains for p63 (a marker that stains the nuclei of prostate basal cells) for this purpose. Several investigators have demonstrated that immunostaining for P504S, a cytoplasmic protein that is overexpressed in a high percentage of prostate cancers and in many cases of high-grade prostatic intraepithelial neoplasia (PIN), can also be of use in the diagnosis of prostate biopsies. Because of the cytoplasmic localization of P504S and nuclear localization of p63, the authors hypothesized that a cocktail of these two antibodies might allow simultaneous demonstration of P504S and p63 using a single immunostain. In this report the authors describe the successful use of a cocktail of p63/P504S for immunohistochemical staining of prostate tissue. Two different staining approaches were investigated, with essentially identical results. This cocktail localizes P504S in the cytoplasm of prostate carcinoma cells and high-grade PIN and demonstrates the nuclei of prostatic basal cells, providing information on both the status of P504S and the presence or absence of basal cells with a single immunostain. This cocktail can be of great utility in the examination of diagnostically challenging prostate specimens.