P504S is an enzyme in the ß-oxidation of branched-chain fatty acids. Expression of P504S protein is found in prostatic adenocarcinoma but not in benign prostatic tissue. p63, a homolog of the tumor suppressor p53, encodes for different isotypes able to either transactivate p53 reporter genes (TAp63) or act as p53-dominant-negatives. Expression of p63 is detected in prostate basal epithelial nuclei in normal prostate; however, is negative in malignant tumors of the prostate gland. p63 + P504S antibody may be an extremely useful aid in diagnosing prostatic intraepithelial neoplasia (PIN), especially in difficult and limited tissues cases.