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.
|Signal Counts||FISH||Dual ISH|
|HER2 mean count||8.8||5.8|
|HER2 median count||4.2||2.7|
|CEP17 mean count||2.9||2.0|
|CEP17 median count||2.8||1.9|
|HER2 negative||HER2 amplified||Total|