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.
"From a practical point of view, it is important to bear in mind that in many regions of the world the use of ALK inhibitors may not be linked to a specific methodology . Taking into consideration the use of improved IHC protocols, eventual false-positive IHC results are more likely to be an interpretative error rather than a technical error, as has been the case in breast HER2 testing . Because dichotomous scoring has been shown to enhance reproducibility, we must insist in defining such criteria for each clone. "
[Show abstract][Hide abstract] ABSTRACT: Background
Based on the excellent results of the clinical trials with ALK-inhibitors, the importance of accurately identifying ALK positive lung cancer has never been greater. However, there are increasing number of recent publications addressing discordances between FISH and IHC. The controversy is further fuelled by the different regulatory approvals. This situation prompted us to investigate two ALK IHC antibodies (using a novel ultrasensitive detection-amplification kit) and an automated ALK FISH scanning system (FDA-cleared) in a series of non-small cell lung cancer tumor samples.
Forty-seven ALK FISH-positive and 56 ALK FISH-negative NSCLC samples were studied. All specimens were screened for ALK expression by two IHC antibodies (clone 5A4 from Novocastra and clone D5F3 from Ventana) and for ALK rearrangement by FISH (Vysis ALK FISH break-apart kit), which was automatically captured and scored by using Bioview's automated scanning system.
All positive cases with the IHC antibodies were FISH-positive. There was only one IHC-negative case with both antibodies which showed a FISH-positive result. The overall sensitivity and specificity of the IHC in comparison with FISH were 98% and 100%, respectively.
The specificity of these ultrasensitive IHC assays may obviate the need for FISH confirmation in positive IHC cases. However, the likelihood of false negative IHC results strengthens the case for FISH testing, at least in some situations.
PLoS ONE 09/2014; 9(9):e107200. DOI:10.1371/journal.pone.0107200 · 3.23 Impact Factor
"These authors argue that primary FISH testing is more cost effective than the evaluation of all IHC-positive patients associated with FISH. The robustness of HER2 FISH was also illustrated by Grimm et al.  that described 4% of discordant tests presenting a positive IHC and a negative FISH and explained this discordance more by interpretative errors than by a technical error. The USA pathological practice currently uses FISH as the primary HER2 screening test and IHC as the control test. "
[Show abstract][Hide abstract] ABSTRACT: Aims. The differences between the 2007 and the 2013 ASCO/CAP HER2 guidelines have been compared. We also discussed the potential consequences in our pathological practice. Material and Methodology. 189 HER2 fluorescence in situ hybridisation (FISH) tests were performed from 1016 preliminary HER2 immunohistochemical tests (IHC). All cases were reviewed and reclassed following the 2007 and 2013 ASCO/CAP recommendations. Results.
The 2013 version decreased false-negative IHC (3/118 versus 1/54, P = ns) and created more 2+ IHC (40/186 versus 89/186, P = 0.001) or more 3+ IHC (9/186 versus 39/186, P = 0.001). One false-positive IHC was described for the 2013 version (0/9 versus 1/39, P = ns). Equivocal FISH was reduced (8/186 versus 2/186, P = ns). An estimation based on our data for 1000 patients showed a rise of our FISH tests for the control of 2+ IHC (180 tests for the 2007 version versus 274 tests for the 2013 version or FISH work overflow is +52%) and for the control of 2+/3+ IHC (300 for the 2007 version versus 475 for the 2013 version or FISH work overflow is +58%). Conclusions. The new 2013 ASCO/CAP guidelines have detected more HER2 positive cases but have increased the number of FISH tests.
"Of the 14 IHC cases that could not be successfully adjudicated, 64 % were classified as 2+. Circumferential distribution and character (intensity, granularity) of cell staining, rather than quantity of stained cells, was the main reason for discordance among the round-robin pathologists, similar to what was reported in a recent HER2 proficiency testing study . The 12 non-adjudicated FISH cases had HER2:CEP17 FISH ratios with an average of 1.88 (range 1.13–2.45) "
[Show abstract][Hide abstract] ABSTRACT: A comprehensive, blinded, pathology evaluation of HER2 testing in HER2-positive/negative breast cancers was performed among three central laboratories. Immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH) analyses were performed on 389 tumor blocks from three large adjuvant trials: N9831, BCIRG-006, and BCIRG-005. In 123 cases, multiple blocks were examined. HER2 status was defined according to FDA-approved guidelines and was independently re-assessed at each site. Discordant cases were adjudicated at an on-site, face-to-face meeting. Results across three independent pathologists were concordant by IHC in 351/381 (92 %) and FISH in 343/373 (92 %) blocks. Upon adjudication, consensus was reached on 16/30 and 18/30 of discordant IHC and FISH cases, respectively, resulting in overall concordance rates of 96 and 97 %. Among 155 HER2-negative blocks, HER2 status was confirmed in 153 (99 %). In the subset of 102 HER2-positive patients from N9831/BCIRG-006, primary blocks from discordant cases were selected, especially those with discordant test between local and central laboratories. HER2 status was confirmed in 73 (72 %) of these cases. Among 118 and 113 cases with IHC and FISH results and >1 block evaluable, block-to-block variability/heterogeneity in HER2 results was seen in 10 and 5 %, respectively. IHC−/FISH− was confirmed for 57/59 (97 %) primary blocks from N9831 (locally positive, but centrally negative); however, 5/22 (23 %) secondary blocks showed HER2 positivity. Among 53 N9831 patients with HER2-normal disease adjudicated as IHC−/FISH—(although locally positive), there was a non-statistically significant improvement in disease-free survival with concurrent trastuzumab compared to chemotherapy alone (adjusted hazard ratio 0.34; 95 % CI, 0.11–1.05; p = 0.06). There were similar agreements for IHC and FISH among pathologists (92 % each). Agreement was improved at adjudication (96 %). HER2 tumor heterogeneity appears to partially explain discordant results in cases initially tested as positive and subsequently called negative.
Electronic supplementary material
The online version of this article (doi:10.1007/s10549-013-2444-y) contains supplementary material, which is available to authorized users.
Breast Cancer Research and Treatment 02/2013; 138(1):99-108. DOI:10.1007/s10549-013-2444-y · 3.94 Impact Factor
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