Comparison of immunohistochemistry by automated cellular imaging system (ACIS) versus fluorescence in-situ hybridization in the evaluation of HER-2/neu expression in primary breast carcinoma

Aims : Immunohistochemistry (IHC) and fluorescence in-situ hybridization (FISH) are both commonly used assays for evaluation of HER-2/neu status in breast cancer. However, there is still no consensus on which method is most predictive of patient response to HerceptinTM. Recently, the automated cellular imaging system (ACIS)TM has been shown to improve the accuracy and reproducibility in scoring IHC. Our aim was to compare the results of HER-2/neu expression and gene amplification in the same patients by IHC using the ACISTM system and by FISH. Methods and results : Two hundred and forty-seven breast cancer cases were studied. The concordance rate between IHC-ACIS (≥ 2.2) and FISH (≥ 2.0) was 94%. Fifteen patients were discordant; three had borderline FISH values and three had borderline IHC values. The other nine discordant cases consisted of five IHC-ACIS+, FISH– and six IHC-ACIS–, FISH+. HER-2/neu overexpression was more common in tumours that were high-grade, aneuploid, progesterone receptor and bcl-2 negative, with MIB-1 > 10%. Conclusion : HER-2/neu assessment by the ACIS is reliable, rapid and inexpensive, and correlates highly with results obtained by FISH.