[1017] Evaluation of Erg Expression in Isolated High Grade Prostatic Intraepithelial Neoplasia (HGPIN) and Benign Prostate Glands

Jennifer N Stall, Nallasivam Palanisamy, Javed Siddiqui, Arul M Chinnaiyan, Scott A Tomlins, Lakshmi P Kunju. University of Michigan, Ann Arbor, MI

Background: ETS gene fusions (most commonly TMPRSS2:ERG) have been identified in approximately 50% of PSA-screened prostate cancers (PCA). By FISH, ERG rearrangements are also present in approximately 15% of high grade prostatic intraepithelial neoplasia (HGPIN), always adjacent to ERG rearranged PCA. As IHC studies have shown variable rates of ERG+ HGPIN (29-52%) in different cohorts, we studied the rate of ERG positivity in isolated HGPIN and benign prostate glands.
Design: From a retrospective cystoprostatectomy cohort, foci of isolated HGPIN (n=67) from 17 cases without PCA (54 slides), HGPIN with incidental PCA from 10 cases (32 slides), and benign prostate from 10 cases (10 slides) were stained with an anti-ERG antibody (clone EPR3864). An additional 55 needle biopsy cores from 5 benign cases with follow-up transperineal mapping biopsy (3/5 cases with PCA on the follow-up biopsy) were also stained for ERG. Staining of endothelial cells was used as an internal positive control and nuclear ERG staining was scored as positive or negative.
Results: Amongst men without PCA on cystoprostatectomy, 3 of 65 (4.5%) foci of isolated HGPIN were ERG+ (one of which had adjacent ERG+ small atypical glands). Amongst men with incidental PCA on cytsoprostatectomy, ERG staining was observed in 1 of 20 (5%) foci of isolated HGPIN (which had adjacent ERG+ small atypical glands) and 2 of 18 (11%) HGPIN foci adjacent to PCA (both with adjacent ERG+ PCA); 1 of 10 (10%) PCA without adjacent HGPIN was ERG+. Amongst all 96 sections and 55 needle biopsy cores, only 2 morphologically benign glands were ERG+, one adjacent to cancer and one in the same section as cancer.
Conclusions: Truly isolated HGPIN is rarely ERG+, in contrast to published rates in HGPIN adjacent to cancer (29-52%), and ERG+ benign prostate glands are exceedingly rare. These findings further support ERG staining as being highly specific for prostatic adenocarcinoma. ERG+ isolated HGPIN in diagnostic biopsies suggests unsampled carcinoma, which may warrant closer clinical follow-up and/or evaluation.
Category: Genitourinary (including renal tumors)

Monday, March 19, 2012 9:30 AM

Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 134, Monday Morning


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