Publication Year: 2000 Visited: 38

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Comparison of Fluorescence in Situ Hybridization (FISH) and Immunohistochemistry (IHC) in Determining HER-2/neu Status in Breast Cancer Patients. Alexander Starr, K Bloom, D Oleske, M A Cobleigh, Rush Cancer Institute, Chicago, IL.

Purpose: To compare fluorescence in situ hybridization and immunohistochemistry determination of HER-2/neu status in breast cancer. Materials and Methods: Between 1998–1999, 65 primary operable breast cancers greater than 1 cm in size, operated at Rush Presbyterian St. Lukes's Medical Center were evaluated by IHC and FISH for HER-2/neu. Specimens were formalin-fixed and paraffin embedded. FISH was performed using the PathVysion^TM kit (Vysis) in a laboratory certified as proficient in this procedure. Results were expressed as a ratio of number of copies of the HER-2/neu gene to the number of chromosome 17 centromeric markers, with a ratio of greater than 1.8 being positive. IHC was performed using the HercepTest^TM kit (DAKO) and the results were scored on a 0 to 3+ scale. Specimens that stained 2+ or 3+ according to the kit definition were considered positive. Results: HER-2/neu was amplified by FISH in 16.9% of cases; 33.8% were HER-2/neu positive by IHC. Concordance between FISH and IHC was seen in 52 of 65 cases (80.0%, p<.001 Fisher's). When results were compared, 1 case interpreted as negative by IHC (scored 1+) was amplified by FISH. Furthermore, 12 cases interpreted as non-amplified by FISH, were scored positive by IHC; only 1 of these 12 cases was scored 3+, while 11/12 were 2+. Conclusions: IHC is more likely to be positive than FISH when evaluating HER-2/neu status in breast cancer.