Various immunohistochemical stains, including prostate-specific antigen (PSA), prostate specific acid phosphatase/prostatic acid phosphatase (PSAP/PAP), NKX3.1, P501S, prostate-specific membrane antigen (PSMA), androgen receptor (AR), and alpha methyacyl CoA racemase (AMACR), are available, which can help to differentiate prostatic adenocarcinoma from carcinomas from other organs. This evidence concerns the gene KLK3 and prostate adenocarcinoma.