Achieving 95% Cross-Methodological Concordance in HER2 Testing Causes and Implications of Discordant Cases
ABSTRACT We were interested in determining our concordance between fluorescence in situ hybridization (FISH) and a previously validated immunohistochemical HER2 assay to identify possible reasons for discordance and to determine if all reasons for discordance were addressed by the American Society of Clinical Oncology/College of American Pathologists guidelines. We reviewed 697 cases (2004-2007) in which HER2 immunohistochemical and FISH testing were concurrently done. Overall concordance between nonequivocal immunohistochemical and FISH results was 96%. Of the 19 discordant cases, 13 (68%) were interpreted as positive immunohistochemically but negative by FISH. The primary reason for this discordance was immunohistochemical interpretation. Weak stain intensity, granular staining, and interpretation in areas of crush artifact were identified as the most common issues. Of the 6 cases interpreted as immunohistochemically negative and FISH-positive, 2 were from patients known to be receiving trastuzumab at the time of biopsy, 1 was very close to the FISH equivocal category, and 4 cases had fewer than 1.5 CEP17 signals per cell (1 patient in this group was also receiving trastuzumab). Focusing on issues with HER2 immunohistochemical interpretation can improve concordance rates for immunohistochemically positive cases, but biologic reasons may explain some discordant immunohistochemically negative cases.
- American Journal of Clinical Pathology 08/2010; 134(2):183-4. DOI:10.1309/AJCP6VZ8YHMZNNED · 3.01 Impact Factor
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ABSTRACT: In 2009, a College of American Pathologists expert panel published supplemental HER2 testing recommendations suggesting that cases with between 5% and 50% individual cells amplified by fluorescence in situ hybridization be reported as "heterogeneous for HER2 gene amplification." We examined the implications of applying these recommendations to clinical practice in 1,329 consecutive breast cancer cases. By ratio criteria, 23.2% of cases met the proposed criteria for heterogeneity, of which 81.6% were not amplified and 15.5% were equivocal by standard criteria. In contrast, the proposed criteria based on HER2 signals per cell classified only 6.5% of cases as heterogeneous, of which only 8% (7/87) were not amplified and 79% (69/87) were equivocal by standard criteria. These results show that the 2 proposed criteria sets are not equivalent and that the ratio-based definition results in large numbers of nonamplified cases being classified as heterogeneous. Further definition of optimal criteria with clinical relevance is needed before HER2 heterogeneity reporting is adopted in routine practice.American Journal of Clinical Pathology 12/2011; 136(6):864-71. DOI:10.1309/AJCPXTZSKBRIP07W · 3.01 Impact Factor
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ABSTRACT: Valid determination of HER2 status is a prerequisite to establish an adequate treatment strategy for breast cancer patients, regardless of the disease stage. The goal of this study was to examine the feasibility of the newly developed silver-enhanced in situ hybridization (SISH) technique as an alternative to fluorescence in situ hybridization (FISH) for HER2 assay in primary invasive breast cancer. FISH and SISH for HER2 amplification were performed using tissue microarray. Both methods were used in 257 consecutive primary breast cancers. HER2 amplification was observed in 62 (23.1%) of a total of 257 breast cancers based on SISH. Of the 257 breast cancers measured using both methods, the results of the two methods were consistent in 248 (concordance, 96.5%; kappa=0.903). When we compared HER2 amplification in the primary tumor with the metastatic lymph nodes of the same patients, HER2 amplification was observed in nine cases (14.0%) out of 64 cases in which HER2 was not amplified in the primary tumors. In contrast, HER2 status was completely preserved in metastatic lymph nodes showing HER2 amplification in the primary tumor. These results indicate that SISH can be a feasible alternative to FISH in the clinical setting. In node-positive breast cancer, confirmation of the HER2 status of the metastatic lymph nodes appears to be mandatory, regardless of the HER2 status of the primary tumors.12/2011; 14(4):276-82. DOI:10.4048/jbc.2011.14.4.276