Detection of ERG gene rearrangements and PTEN deletions in unsuspected prostate cancer of the transition zone.

To assess the incidence of ERG rearrangements and PTEN deletions in a group of prognostically favorable PCA tumors of the transition zone (TZ). We interrogated 54 unsuspected PCA tumors using fluorescence in-situ hybridization for ERG rearrangements and PTEN deletions. ERG rearrangements were detected in 6/47 (12.7%) cases with 4/6 (66%) occurring by deletion. PTEN deletions were detected in 9/47 (19.1%) cases with only 3/47 (6.4%) having both PTEN losses and ERG rearrangements (p = 0.07). Only ERG rearrangements were associated with higher tumor volume > 5% (p = 0.04); PTEN deletions showed similar trends (p = 0.06). None of the markers showed association with Gleason score. In conclusion, although TZ and peripheral zone tumors share similar molecular etiologies, they exhibit differences in the rates of ERG and PTEN aberrations. The differences of ERG and /or PTEN genetic aberrations in TZ tumors may point toward a subset of tumors with adverse behavior. Additional studies implementing ERG and PTEN tissue-based FISH assays in tumors of the TZ are warranted to substantiate the potential clinical value of these biomarkers in the management of men with incidental PCA.