Putting the colours into chromogenicin situ hybridization (CISH)

Instant-quality fluorescence in-situ hybridization as a new tool for HER2 testing in breast cancer: a comparative study

AIMS

HER2 instant-quality fluorescence in-situ hybridization (IQFISH) is a new fluorescence in-situ hybridization (FISH) assay developed with a non-toxic buffer that reduces the hybridization time to 1-2 h, enabling a turnaround time of 3 h 30 min from dewax to counting. The aim of this study was to compare assessment of HER2 status using IQFISH and assessment using standard FISH.

METHODS AND RESULTS

We selected 160 breast cancer samples according to their HER2 status as determined by immunohistochemistry (IHC) in a retrospective multicentre cohort (40 cases in each scoring category, i.e. 0/1+/2+/3+). Each participating site (n = 5) constructed its tissue microarray (TMA) of 32 archival cases and sent it to the central site (site 1). HER2 IHC, HER2 FISH and HER2 IQFISH were performed blindly at site 1. IQFISH provided excellent quality signals without any background staining, thus allowing excellent reading conditions even on TMA. Statistical analysis showed almost perfect agreement between IQFISH and FISH (99.3%, κ = 0.98). The only discordant case was an equivocal one with an HER2/CEP17 ratio near the ASCO/CAP cut-off.

CONCLUSIONS

The highly concordant data support IQFISH as a useful alternative to FISH, allowing reliable assessment of HER2 status. Use of this method could lead to reporting of HER status to the oncologist within a day.

Histochemistry as a tool in morphological analysis: a historical review

Histochemistry has an interesting history, extending back to ancient times, in some ways. Man has long had a desire to understand the workings of the human body and the roles that various "humors" or chemicals have in those processes. This review traces the evolution of histochemistry as an investigative and diagnostic discipline, beginning with the efforts of medicinal chemists and extending through a period in which histology was increasingly paired with biochemistry. Those developments served as the underpinnings for an eventual marriage of microscopy, chemistry, immunology, and molecular biology, as realized in the current practice of anatomical pathology.

[HER-2 oncogene amplification assessment in invasive breast cancer by dual-color in situ hybridization (dc-CISH): a comparative study with fluorescent in situ hybridization (FISH)]

OBJECTIVES

The amplification of the gene encoding for the human epidermal growth factor receptor 2 (HER-2 oncogene), located on chromosome 17 (17q21-q22), or the overexpression of this receptor have prognostic and therapeutic implications in invasive breast cancer. An evaluation of the HER-2 status by immunohistochemistry (IHC) is performed on all invasive breast cancer cases. Fluorescent in situ hybridization (FISH) is considered as the gold standard for the detection of HER-2 gene amplification for IHC equivocal cases (score 2+). A more recent in situ hybridization technique, the dual-color chromogenic in situ hybridization (dc-CISH), has been proposed as an alternative to FISH. The aim of this study was to measure the correlation between dc-CISH and FISH for HER-2 oncogene amplification assessment in invasive breast cancer.

METHODS AND RESULTS

We built four tissue micro-array (TMA) blocs with 100 breast invasive cancer cases that had been previously tested by IHC for HER-2 detection: 10 score 0 cases, 10 score 3+cases, 39 score 1+and 41 score 2+cases. Both FISH and dc-CISH techniques were applied on all TMA cases as well as on two additional slides serving as controls. Interpretation of dc-CISH was carried out by a pathologist using an optical microscope. For FISH, the interpretation was done by a professional from the medical genetics department using a fluorescent microscope linked to a computer system for image capturing and analysis. The interpretation of the HER-2/CEN-17 ratio for both tests was in accordance with the values of the updated recommendations from the Canadian National Consensus Meeting on HER-2/neu testing in breast cancer and from the ASCO/CAP. Among the 100 cases initially included in the study, eight were excluded from the analysis due to sampling or technical flaws. From the 92 remaining cases, we obtained a concordance of 97.8% (90/92 cases) between the two techniques (Kappa coefficient 0.97, 95% confidence interval). The correlation coefficient (rho) between ratios was estimated at 0.57.

CONCLUSION

This study shows a strong concordance between FISH and dc-CISH techniques and indicates that dc-CISH is a good alternative method for HER-2 gene amplification assessment in breast cancer.

Out of the darkness and into the light: bright field in situ hybridisation for delineation of ERBB2 (HER2) status in breast carcinoma

Assessment of ERBB2 (HER2) status in breast carcinomas has become critical in determining response to the humanised monoclonal antibody trastuzumab. The current joint College of American Pathologists and the American Society of Clinical Oncology guidelines for the evaluation of HER2 status in breast carcinoma involve testing by immunohistochemistry and fluorescence in situ hybridisation (FISH). However, neither of these modalities is without limitations. Novel bright field in situ hybridisation techniques continue to provide viable alternatives to FISH testing. While these techniques are not limited to evaluation of the HER2 gene, the extensive number of studies comparing bright field in situ techniques with other methods of assessing HER2 status allow a robust evaluation of this approach. Analysis of the literature demonstrates that, when used to assess HER2 gene status, bright field in situ hybridisation demonstrates excellent concordance with FISH results. The average percentage agreement in an informal analysis of studies comparing HER2 amplification by chromogenic in situ hybridisation with FISH was 96% (SD 4%); kappa coefficients ranged from 0.76 to 1.0. Although a much smaller number of studies are available for review, similar levels of concordance have been reported in studies comparing HER2 amplification by methods employing metallography (silver in situ hybridisation) with FISH. A summary of the advancements in bright field in situ hybridisation, with focus on those techniques with clinical applications of interest to the practicing pathologist, is presented.