Alpha methylacyl-CoA-racemase (AMACR), also known as p504s is an enzyme involved in the metabolism of branched-chain fatty acids. p504s is expressed in various normal tissues and carcinomas, while it is overexpressed over 30-fold in  prostate carcinoma compared to benign glandular tissues1. When p504s is overexpressed in atypical glands without basal cells, it establishes a diagnosis of prostatic carcinoma. High-grade prostatic intraepithelial neoplasia, atypical adenomatous hyperplasia and urothelial carcinoma may also express p504s.