ERG and prostate adenocarcinoma: Normal and benign prostate tissues, as well as prostatic intraepithelial neoplasia lesions, lack the expression of ERG, whereas expression of TMPRSS2–ERG fusion mRNAs occurs uniquely in prostate adenocarcinoma because of the fusion of a promoter/enhancer region of an androgen-responsive prostate-specific serine protease 2-encoding gene, TMPRSS2, to the v-ets erythroblastosis virus E26 oncogene homologue, ERG, or the ETS variant 1 gene, ETV1 (Tomlins et al, 2005; Narod et al, 2008), and over 20 other gene fusion variants (Perner et al, 2006; Mehra et al, 2007; Tu et al, 2007).