[1611] Added Value of ERG to PIN Cocktail for Evaluation of Atypical Small Acinar Proliferations (ASAP) of Prostate

Elena E Chang, Daniel J Luthringer, Mariza de Peralta-Venturina, Mahul B Amin. Cedars-Sinai Medical Center, Los Angeles, CA

Background: High correlation with prostate cancer (PCa) potentiates ERG as an additional marker to the PIN cocktail in determining ASAP versus PCa diagnosis. ERG is positive in 11-16% of atypical biopsies, but previous studies do not directly address the added diagnostic value of ERG to the PIN cocktail. This study determines the impact of ERG on the final diagnosis beyond assessment based on H&E and PIN cocktail (HE+PIN).
Design: Biopsies from 7/2010-5/2012 diagnosed as ASAP after HE+PIN (PINATYP excluded) were stained retrospectively with ERG(EPR3864). All cores with ASAP by H&E received from 6/2012-9/2012 were evaluated with PIN cocktail and ERG results. Subsequently, all ERG-positive cases from both arms were independently reviewed by 3 urologic pathologists to render diagnostic impression based on H&E only, HE+PIN, and HE+PIN+ERG evaluation. A negative ERG result is non-contributory.
Results: In the 107 retrospective cases, ERG was negative in 97. Of the 10(9%) ERG-positive cases, 3 cases by majority and 1 unanimously were upgraded from ASAP to PCa based on HE+PIN evaluation given absent basal cells and variably upregulated racemase. After HE+PIN+ERG, 1 case was upgraded to PCa based on ERG staining while 5 remained ASAP: 4 due to presence of rare basal cells despite increased racemase, 1 considered insufficient malignant histology by majority. In the prospective arm, ERG was positive in 3/24(13%). After HE+PIN, converted diagnoses were 13(54%) PCa and 5(21%) benign. One PCa was ERG-positive; benign cases were all ERG-negative. Of the remaining 7(29%) ASAP cases, 2 were positive for ERG: 1 was converted to PCa, the other remained ASAP due to weak inconsistent staining in suspicious glands and weak positivity in morphologically benign glands. In total, ERG was positive in 10%(13/131) of ASAPs; ERG impacted the diagnosis in 1.5%(2/131) of ASAPs.
Conclusions: The difficulty in achieving unanimous consensus diagnosis highlights the subjective aspect of HE+PIN interpretation and ASAP designation. ERG positivity adds to the malignant quality of atypical glands, but whether this contribution to histology and PIN exceeds the threshold for diagnosis of PCa varies. Regardless, overall ERG positivity in ASAP is low, and even within ERG-positive cases, the same conclusion was often achieved by just HE+PIN. ASAPs with at least rare basal cells were never designated as PCa, and it is unlikely ERG would change this. The limited added utility should be considered with costs and resources for its upfront use in routine evaluation of ASAP within standard practice.
Category: Kidney (does not include tumors)

Tuesday, March 5, 2013 1:00 PM

Poster Session IV # 178, Tuesday Afternoon


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