[1000] Immunohistochemical Evaluation of TMPRSS2-ERG Gene Fusion in Focal Prostatic Atrophy

Ana CS Piaza, Luciana Meirelles, Leandro LLL Freitas, Larissa BE Costa, Joao FL Bonfitto, Betina L Diniz, Paola H Poletto, Athanase Billis. School of Medicine, University of Campinas (Unicamp), Campinas, SP, Brazil

Background: Focal prostatic atrophy is one of the most frequent histologic mimics of prostatic adenocarcinoma. The most common variant that causes difficulty in the differential diagnosis with adenocarcinoma is partial atrophy. A possible association of atrophy with adenocarcinoma is still controversial. The TMPRSS2-ERG fusion has been identified as a common chromosomal rearrangement which occurs early in the development of 50% of prostate cancer. Recently, a specific anti-ERG antibody is available that has 95.7% sensitiviy and 96.5% specificity for detecting ERG protein expression, thus serving as a useful marker for ERG rearrangements using immunohistochemistry. In this study we used this antibody in all variants of focal prostatic atrophy.
Design: We studied sections showing only focal atrophy from the surgical specimens of 12 patients submitted to radical prostatectomy. Focal prostatic atrophy was classified into partial and complete. The latter subtyped into simple, hyperplastic (or postatrophic hyperplasia) and sclerotic. The lesions were evaluated by immunohistochemistry for ERG expression (Source: Epitomics; Clone: EPR3864; Pretreatment: EDTA; Dilution: 1:100). Quality control was acessed by examining the nuclei of endogenous endothelial cells as an internal positive control.
Results: In all sections examined no positive cells for ERG expression were seen either in the basal or the secretory compartment in partial or complete atrophy (simple, hyperplastic, or sclerotic) as well as foci of hyperplastic atrophy with chronic inflammation (proliferative inflammatory atrophy). The quality of the staining was adequate evidenced by staining of the nuclei of endothelial cells.


Conclusions: In this study no variant of focal prostatic atrophy showed ERG protein expression evaluated for TMPRSS2-ERG rearrangement by ERG immunostaining. This result seems not to be in favor of a role of TMPRSS2-ERG in a possible association of focal atrophy with prostate adenocarcinoma. Moreover, the results suggest that positive immunohistochemistry for ERG could be a marker to exclude a diagnosis of prostate atrophy.
Category: Genitourinary (including renal tumors)

Wednesday, March 6, 2013 1:00 PM

Poster Session VI # 145, Wednesday Afternoon

 

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