The Equivocally Amplified HER2 FISH Result on Breast Core Biopsy: Indications for Further Sampling Do Affect Patient Management

Department of Pathology, Magee-Womens Hospital, Pittsburgh, PA 15213, USA.
American Journal of Clinical Pathology (Impact Factor: 2.51). 04/2008; 129(3):383-90. DOI: 10.1309/KFKDNK8CENVN24VU
Source: PubMed


To our knowledge, there are no universally accepted, evidence-based guidelines for how to resolve the HER2 status of tumors demonstrating equivocal amplification. The present study was based on 17 breast core biopsy specimens demonstrating invasive carcinoma with equivocal HER2 amplification, defined as an HER2/chromosome 17 centromere ratio of 1.8 to 2.2. Each case had a corresponding resection specimen, on which HER2 immunohistochemical and repeated fluorescence in situ hybridization analyses were performed. A definitive change in HER2 status based on the resection specimen occurred in 10 (59%) of 17 cases, with 4 patients (24%) becoming eligible for trastuzumab therapy and 6 (35%) triaged as ineligible. These results suggest that genetic and protein expression heterogeneity exists in tumors that show low-level HER2 gene copy numbers. For the purposes of uniform clinical management, HER2 status should be evaluated on a larger tumor sample if the core biopsy specimen demonstrates an equivocal result. These results support the recent American Society of Clinical Oncology/College of American Pathologists recommendations for further testing in cases with equivocal HER2 results.

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    • "central comparisons, this refers to the number of specimens graded as positive for HER2 by the local laboratory and confirmed positive in central laboratory; in the central vs. central comparison, this refers to the number of concordant results assessed by 3 pathologists at 3 central laboratories. that there is clinical support for the ASCO/CAP recommendations for resampling and testing HER2 status in cancers that show an equivocal result on initial FISH testing [55]. Other data, however, suggest that the guideline-prescribed change in criteria used to define HER2-positive status may have a negative impact on patient care by restricting access to HER2-tar- geted treatment in patients who could benefit from such treatment. "
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