ERG and prostate carcinoma: ERG rearrangement with TMPRSS2, a prostate-specific transmembrane serine protease regulated by androgens [4], accounts for more than 90% of the fusion-positive cases, being present in about 50% of prostate carcinomas [5] and 20% of the presumed precursor lesion high-grade prostatic intraepithelial neoplasia (HGPIN) [6].