[885] Monoclonal Antibody 6C4 Distinguishes Prostatic Carcinoma from Benign Mimics in Which PIN4 Immunostaining Is Non-Diagnostic

Jaclyn F Hechtman, Guang Q Xiao, Yayoi Kinoshita, Pamela D Unger, David E Burstein. Mount Sinai School of Medicine, New York, NY

Background: 6C4 is a monoclonal antibody to glutamate receptor 2 (GluR2), an excitatory amino acid receptor subunit in the central nervous system. 6C4 reactivity in prostatic tissue has not been previously investigated. Recently, our data have shown that benign prostatic epithelium is strongly reactive for 6C4 while low-grade prostatic carcinoma is negative. Post-atrophic hyperplastic and adenosis-like prostatic glands are common mimics of low-grade prostate carcinoma (PCa). Due to the frequent absence of basal cells on p63 and high molecular-weight cytokeratin (HMCK) immunostain in these mimics, it is not uncommon for them to pose a diagnostic challenge to urologic pathologists, particularly in biopsy specimens. The goal of this study is to assess the utility of 6C4 in the discernment of post-atrophic or adenosis-like prostatic epithelia from low-grade PCa.
Design: 10 prostate sections with post-atrophic or adenosis-like areas were chosen from separate prostatectomy specimens. Each was stained with monoclonal antibody to GluR2 (6C4, gift of J. Morrison, 0.8 microgram/ml) in parallel with PIN4, a triple antibody cocktail against alpha methyl acyl coA racemase (AMACR), Ker903 and p63 (Biocare Medical, CT, USA). Membranous and cytoplasmic staining patterns of 6C4 were considered positive.
Results: Post-atrophic glands were remarkable for architectural and cytologic atypia (Figure 1a; hematoxylin and esoin; original magnification x100). Basal cell markers were negative in all ten cases, and weak or strong positivity for AMACR was seen in the secretory epithelium in 4 of 10 cases (Figure 1b; PIN4 immunostaining; original magnification x100). Uniform and strong positive staining with 6C4 was demonstrated in these glands in all ten cases (Figure 1c; 6C4 immunostaining; original magnification x100).

Conclusions: As seen in other benign prostate glands, the uniform positivity of 6C4 in post-atrophic and adenosis-type glands readily separated them from prostate cancer with low Gleason's score, which are C64 negative. Therefore, 6C4 has a potential diagnostic advantage over PIN4 in distinguishing low-grade PCa from the aforementioned mimics.
Category: Genitourinary (including renal tumors)

Wednesday, March 21, 2012 9:30 AM

Poster Session V # 126, Wednesday Morning


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