ERG Expression in Prostate Needle Biopsy: Potential Diagnostic and Prognostic Implications

To investigate the prognostic and diagnostic value of ERG immunohistochemistry (IHC) in prostate needle biopsy when combined with AMACR-CK5/6. ERG IHC was assessed in 119 consecutive prostate needle biopsies where the dual-stain AMACR-CK5/6 IHC was ordered and in 16 cases with a Gleason score (GS) ≥7. IHC results were evaluated in prostate carcinoma (PCA), high-grade prostatic intraepithelial neoplasia (HGPIN), HGPIN with adjacent atypical glands (PINATYP), atypical/suspicious (ASAP) foci, and benign PCA mimickers. GS, HGPIN, extraprostatic extension, perineural invasion, bilateralism of PCA, largest percent of core, and the overall percent of tissue involved by PCA were recorded. ERG was detected in 36% of PCA, 27% of HGPIN, 13% of ATYP/PINATYP, and none of benign mimickers. ERG-positive HGPIN was strongly associated with ERG-positive PCA in the same core compared with ERG-negative HGPIN (P