Comparison of fluorescence in situ hybridization and dual color chromogenic in situ hybridization for the assessment of HER2 status on core-needle breast cancer biopsies.

Abstract

Abstract Abstract #3015 Background: Core-needle biopsies have been shown to be extremely useful for evaluation of prognostic and predictive markers. In breast cancer patients, this is particularly important in the setting of neoadjuvant chemotherapy. However, it is well known that immunohistochemistry can give conflictive results on small biopsies or core-needle biopsies. This study evaluates the concordance between HER2 gene amplification determined by fluorescence in situ hybridization (FISH) and a new dual color cromogenic in situ hybridization (CISH) in a series of core-needle breast biopsies.
 Material and Methods: A total of 37 invasive breast carcinomas diagnosed on core-nedle breast biopsies were selected from our files. Dual color FISH (Dako, Glostrup) and dual color CISH (Dako, Glostrup) were performed in each case. Scoring of the FISH and CISH slides was identical, counting HER2 and CEN-17 signals from 60 tumour nuclei per case. Finally, the gene to CEN-17 ratio was calculated using the cut-off value of HER2/CEN-17 ratio >2 as amplified.
 Results: All 37 specimens were analyzed successfully by CISH and FISH. A high concordance was found between FISH and CISH in the assessment of HER2 status. 12 cases were amplified and counted easily with both techniques, showing similar ratios. Polysomy was also detected with both techniques in 5 cases with no amplification.
 Discussion: Given the presumed heterogeneous expression of HER2 immunohistochemistry on core-needle biopsies, dual color CISH might be an alternative to FISH in this setting. Moreover, CISH allows for a better concurrent analysis of morphology, which is particularly important when studying small samples. Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 3015.