α-Methylacyl coenzyme A racemase (AMACR Antibody), also known as P504S, is a peroxisomal and mitochondrial enzyme that plays a role in bile acid synthesis and β-oxidation of branched chain fatty acids. In immunohistochemistry, AMACR Antibody has been shown to be a specific marker of prostatic adenocarcinoma. Additionally, prostate glands involved in PIN have been found to express AMACR, whereas AMACR was nearly undetectable in benign glands. AMACR + CK5/14 may be used to assess neoplasia in prostate biopsies. AMACR Antibody stains the majority of prostate cancer; however, AMACR has been shown to stain many other types of carcinomas such as hepatomas, breast carcinomas, pancreatic and islet tumors.