Evaluation of ERG and PTEN protein expression in cribriform architecture prostate carcinomas

ERG and PTEN have been suggested as potential prognostic markers in prostatic adenocarcinoma. We assessed the relationship between ERG and PTEN protein expression in cribriform architecture prostatic carcinomas and adjacent acinar non-cribriform carcinoma and determined the interobserver variability in assessment of these markers. A contemporary cohort of radical prostatectomy cases (n=246) were reviewed and cribriform architecture carcinomas (intraductal carcinoma and cribriform Gleason 4 carcinomas) were identified and confirmed with triple cocktail immunostaining. ERG and PTEN protein expression were independently examined across all carcinoma components by two pathologists. 57 cases were available for immunohistochemistry. ERG protein expression was concordant between the cribriform and non-cribriform acinar carcinomas in 56/57 cases. There was no interobserver discrepancy in ERG assessment. PTEN staining was concordant in 53/57 cases however 33 cases showed heterogeneous staining, most marked in the non-cribriform acinar component. The kappa value for interobserver assessment of PTEN scoring was 0.787 (moderate) with discrepant cases resolved by cooperative review. ERG protein expression shows almost complete concordance (98.2%) across cribriform and non-cribriform prostatic carcinomas. Assessment of this staining is straightforward and consistent between observers. PTEN protein expression is heterogeneous and results in only moderate interobserver agreement. Both staining heterogeneity and interpretation present challenges in analyzing PTEN protein expression.