[108] Dual-Color In Situ Hybridization (Dual ISH) for Evaluation of HER2/Neu (HER2) Amplification in Breast Cancer

Kristine Astvatsaturyan, Shikha Bose. Cedars-Sinai Medical Center, Los Angeles, CA

Background: HER2 amplification is a well recognized prognostic and predictive marker for breast cancer. Amplification is traditionally analyzed by flourescent in situ hybridization (FISH) which is an expensive and laborious procedure that limits widespread use. Dual ISH, a promising alternative to FISH, has recently been FDA approved for HER2 testing in breast cancer. This study is designed to compare Dual ISH to FISH for determining HER2 amplification in breast cancer.
Design: Dual ISH was performed on 51 cases of infiltrating breast carcinomas retrieved from our files using Ventana Medical System's INFORM Her2 Dual ISH DNA Probe Cocktail which detects HER2 copies via silver ISH and CEP17 copies via chromogenic Red ISH in formalin-fixed, paraffin-embedded sections as per the manufacturer's guidelines. All of these cases had been subjected to prior HER2 analysis by FISH using the PathVysion HER2/neu kit (Abbott-Vysis, USA). All protocols were in keeping with the CAP guidelines. Of the 51 cases, 14 were Her2 amplified, 33 were Her2 negative and 4 were Her2 equivocal. Dual ISH was successfully performed in 50 cases which formed the basis of this study. HER2 to CEP 17 ratio was calculated manually for each case. Results were compared.
Results:

Table 1: Comparison of the overall HER2 and CEP17 signal counts obtained by FISH and Dual ISH
Signal CountsFISHDual ISH
HER2 mean count8.85.8
HER2 median count4.22.7
CEP17 mean count2.92.0
CEP17 median count2.81.9




Table 2: Comparison of HER2 results obtained by FISH and Dual ISH
FISHDual ISH
 HER2 negativeHER2 amplifiedTotal
HER2 negative30232
HER2 equivocal404
HER2 amplified01414
Total351550


Although we noticed lower signal counts for both HER2 and CEP17 (Table1) by Dual ISH, HER2 negative and HER2 amplified cases showed 94% and 100% concordance respectively (Table 2). The two HER2 negative cases that were amplified by Dual ISH showed ratios of 2 and 2.1. All four of the HER2 equivocal cases were negative by Dual ISH.
Conclusions: Dual ISH:
is a viable alternative to FISH for evaluation of HER2 status and offers many advantages (light microscopic evaluation, preservation of tissue morphology, capabilities for archiving, re-evaluation and use in retrospective studies).
has a high concordance rate with FISH.
offers lower rates of equivocal results as compared to FISH.
shows lower HER2 and CEP17 signal counts as compared to FISH.
Category: Breast

Tuesday, March 5, 2013 1:00 PM

Poster Session IV # 42, Tuesday Afternoon

 

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