Chromogenic in situ hybridisation (CISH) should be an accepted method in the routine diagnostic evaluation of HER2 status in breast cancer

Progress on deep learning in digital pathology of breast cancer: a narrative review

BACKGROUND AND OBJECTIVE

Pathology is the gold standard criteria for breast cancer diagnosis and has important guiding value in formulating the clinical treatment plan and predicting the prognosis. However, traditional microscopic examinations of tissue sections are time consuming and labor intensive, with unavoidable subjective variations. Deep learning (DL) can evaluate and extract the most important information from images with less need for human instruction, providing a promising approach to assist in the pathological diagnosis of breast cancer. To provide an informative and up-to-date summary on the topic of DL-based diagnostic systems for breast cancer pathology image analysis and discuss the advantages and challenges to the routine clinical application of digital pathology.

METHODS

A PubMed search with keywords ("breast neoplasm" or "breast cancer") and ("pathology" or "histopathology") and ("artificial intelligence" or "deep learning") was conducted. Relevant publications in English published from January 2000 to October 2021 were screened manually for their title, abstract, and even full text to determine their true relevance. References from the searched articles and other supplementary articles were also studied.

KEY CONTENT AND FINDINGS

DL-based computerized image analysis has obtained impressive achievements in breast cancer pathology diagnosis, classification, grading, staging, and prognostic prediction, providing powerful methods for faster, more reproducible, and more precise diagnoses. However, all artificial intelligence (AI)-assisted pathology diagnostic models are still in the experimental stage. Improving their economic efficiency and clinical adaptability are still required to be developed as the focus of further researches.

CONCLUSIONS

Having searched PubMed and other databases and summarized the application of DL-based AI models in breast cancer pathology, we conclude that DL is undoubtedly a promising tool for assisting pathologists in routines, but further studies are needed to realize the digitization and automation of clinical pathology.

Targeted therapeutic options and future perspectives for HER2-positive breast cancer

Over the past 2 decades, there has been an extraordinary progress in the regimens developed for the treatment of human epidermal growth factor receptor 2 (HER2)-positive breast cancer. Trastuzumab, pertuzumab, lapatinib, and ado-trastuzumab emtansine (T-DM1) are commonly recommended anti-HER2 target agents by the U.S. Food and Drug Administration. This review summarizes the most significant and updated research on clinical scenarios related to HER2-positive breast cancer management in order to revise the guidelines of everyday clinical practices. In this article, we present the data on anti-HER2 clinical research of neoadjuvant, adjuvant, and metastatic studies from the past 2 decades. We also highlight some of the promising strategies that should be critically considered. Lastly, this review lists some of the ongoing clinical trials, findings of which may soon be available.

Evaluating HER2 Gene Amplification Using Chromogenic In Situ Hybridization (CISH) Method In Comparison To Immunohistochemistry Method in Breast Carcinoma

BACKGROUND:

In patients with breast cancer, HER2 gene expression is of a great importance in reacting to Herceptin treatment. To evaluate this event, immunohistochemistry (IHC) has been done routinely on the basis of scoring it and so the patients were divided into 4 groups. Lately, as there have been disagreements about how to treat score 2 patients, chromogenic in situ hybridization (CISH) and florescence in situ hybridization (FISH) are introduced. Since CISH method is more convenient than FISH for gene amplification study, FISH has been substituted by CISH.

AIM:

The current study is conducted in order to investigate whether using CISH is a better method comparison to IHC method for determines HER2 expression in patients with breast cancer in.

METHODS:

In this cross-sectional descriptive analytical study, information of 44 female patients with invasive ductal breast cancer were gathered from Imam Reza and Omid Hospital in Mashhad. IHC staining was done for all patients in order to determine the level of HER2 expression, and after scoring them into 4 groups of 0, +1, +2 and +3, CISH staining was carried out for all 4 groups. At the end, results from both methods were statistically evaluated using SPSS software V.22.0.

RESULTS:

The average age of patients was 50.2 with the standard deviation of 10.96. Using IHC method was observed that 2.6% (1 patient), 26.3% (10 patients), 65.8% (25 patients) and 5.3% (2 patients) percentage of patients had scores of 0, +1, +2 and +3. On the other hand, CISH method showed 36 patients (90%) with no amplifications and 4 (10%) with sever amplifications. In a comparative study using Fisher’s exact test (p = 0.000), we found a significant relation between IHC method and CISH method indicating that all patients showing severe amplifications in CISH method, owned scores of +2 and +3 in IHC method.

CONCLUSION:

According to the present study and comparing the results with similar previous studies, it can be concluded that CISH method works highly effective in determining HER2 expression level in patients with breast cancer. This method is also able to determine the status of patients with score +2 in IHC for their treatment with herceptin.

Comparative Performance of Breast Cancer Human Epidermal Growth Factor Receptor 2 Fluorescence In Situ Hybridization and Brightfield In Situ Hybridization on College of American Pathologists Proficiency Tests

CONTEXT.—

Fluorescence in situ hybridization (FISH) and brightfield in situ hybridization (ISH) are 2 clinically approved laboratory methods for detecting ERBB2 (HER2) amplification in breast cancer.

OBJECTIVE.—

To compare the performance of FISH and brightfield ISH on proficiency testing administered by the College of American Pathologists Laboratory Accreditation Program.

DESIGN.—

Retrospective review was performed on 70 tissue core samples in 7 separate proficiency testing surveys conducted between 2009 and 2013.

RESULTS.—

The samples included 13 consensus-amplified tissue cores, 53 consensus-nonamplified cores, and 4 cores that did not reach consensus for FISH and/or brightfield ISH. There were 2552 individual responses for FISH and 1871 individual responses for brightfield ISH. Consensus response rates were comparable for FISH (2474 of 2524; 98.0%) and brightfield ISH (2135 of 2189; 97.5%). The FISH analysis yielded an average HER2 copy number per cell that was significantly higher (by 2.86; P = .02) compared with brightfield ISH for amplified cores. For nonamplified cores, FISH yielded slightly, but not significantly, higher (by 0.17; P = .10) HER2 copy numbers per cell. There was no significant difference in the average HER2 to control ratio for either consensus-amplified or consensus-nonamplified cores. Participants reported "unable to analyze" more frequently for brightfield ISH (244 of 2453; 9.9%) than they did for FISH (160 of 2684; 6.0%).

CONCLUSIONS.—

Our study indicates a high concordance rate in proficiency testing surveys, with some significant differences noted in the technical performance of these assays. In borderline cases, updated American Society of Clinical Oncology/College of American Pathologists cutoff thresholds that place greater emphasis on HER2 copy number per cell could accentuate those differences between FISH and brightfield ISH.

Evaluation of HER2 Protein Expression Using 2 New Monoclonal Antibodies

This study describes the performance of 2 new mouse anti-HER2 monoclonal antibodies (Abs), clones 33F and 410G, in evaluating HER2 overexpression in a series of 123 invasive breast carcinoma cases. In-house immunohistochemistry (IHC) was performed and the results were compared with those for the SP3 and A0485 anti-HER2 Abs. Chromogenic in situ hybridization was used to detect ERBB2 amplification and its concordance with IHC was analyzed. Comparison of IHC results for 33F with SP3 and A0485 yielded concordance rates (K) of 0.81 and 0.75, respectively; the same concordance rates were found when comparing results for 410G with SP3 and A0485. Compared with SP3 and A0485, 33F and 410G specificities were 98.6% and 98.6%, and 100% and 100%, respectively, whereas the sensitivities were 80% and 74.1%, and 78% and 72.2%, respectively. The K values between 33F and 410G HER2+ expression and chromogenic in situ hybridization-positive amplification were 1 and 0.96, respectively. These concordance rates were reproduced in another production batch (K=0.96 and K=0.96). Together, these results show that the tested monoclonal Abs would be well suited for detecting HER2 protein overexpression by IHC.

Evaluation of chromogenic in situ hybridization for the determination of monosomy 3 in uveal melanoma

CONTEXT

Loss of 1 copy of chromosome 3 is considered a significant indicator of metastatic dissemination in uveal melanoma. Fresh or paraffin-embedded tumor tissue is most commonly used for current cytogenetic techniques for determining chromosome 3 status in uveal melanoma and often requires referral to an external specialist laboratory for analysis.

OBJECTIVES

To assess the chromogenic in situ hybridization assay for detecting chromosome 3 alterations using frozen tumor imprints and to compare the results obtained with those obtained by standard fluorescence in situ hybridization or single-nucleotide polymorphism array techniques.

DESIGN

Chromogenic in situ hybridization was performed on 52 frozen uveal melanoma tumor imprints. The genetic status of 26 of the 52 cases had been determined previously by fluorescence in situ hybridization (group 1); the status of 26 cases had been determined using single-nucleotide polymorphism array (group 2).

RESULTS

Chromogenic in situ hybridization was successfully performed on 48 of 52 tumor imprints. Chromogenic in situ hybridization showed excellent agreement in all 24 cases determined by fluorescence in situ hybridization (100% concordance; κ = 1; P < .001; 95% confidence interval, 100%-100%), and disagreed in 4 of the 24 cases previously studied by single-nucleotide polymorphism array (83% concordance; κ = 0.67; P < .001; 95% confidence interval, 95%-39%). All 4 discordant cases were classified as disomic for chromosome 3 by chromogenic in situ hybridization and monosomic by SNP array. On histologic examination, the 4 discordant cases corresponded to 2 mixed cell tumors and 2 spindle cell tumors.

CONCLUSIONS

Chromogenic in situ hybridization using tumor imprints is a reliable technique for determining chromosome 3 status in uveal melanoma. Furthermore, it can also be easily integrated into a routine histopathology laboratory.

Recommendations for human epidermal growth factor receptor 2 testing in breast cancer: American Society of Clinical Oncology/College of American Pathologists clinical practice guideline update

PURPOSE

To update the American Society of Clinical Oncology (ASCO)/College of American Pathologists (CAP) guideline recommendations for human epidermal growth factor receptor 2 (HER2) testing in breast cancer to improve the accuracy of HER2 testing and its utility as a predictive marker in invasive breast cancer.

METHODS

ASCO/CAP convened an Update Committee that included coauthors of the 2007 guideline to conduct a systematic literature review and update recommendations for optimal HER2 testing.

RESULTS

The Update Committee identified criteria and areas requiring clarification to improve the accuracy of HER2 testing by immunohistochemistry (IHC) or in situ hybridization (ISH). The guideline was reviewed and approved by both organizations.

RECOMMENDATIONS

The Update Committee recommends that HER2 status (HER2 negative or positive) be determined in all patients with invasive (early stage or recurrence) breast cancer on the basis of one or more HER2 test results (negative, equivocal, or positive). Testing criteria define HER2-positive status when (on observing within an area of tumor that amounts to >10% of contiguous and homogeneous tumor cells) there is evidence of protein overexpression (IHC) or gene amplification (HER2 copy number or HER2/CEP17 ratio by ISH based on counting at least 20 cells within the area). If results are equivocal (revised criteria), reflex testing should be performed using an alternative assay (IHC or ISH). Repeat testing should be considered if results seem discordant with other histopathologic findings. Laboratories should demonstrate high concordance with a validated HER2 test on a sufficiently large and representative set of specimens. Testing must be performed in a laboratory accredited by CAP or another accrediting entity. The Update Committee urges providers and health systems to cooperate to ensure the highest quality testing.

Recommendations for human epidermal growth factor receptor 2 testing in breast cancer: American Society of Clinical Oncology/College of American Pathologists clinical practice guideline update

PURPOSE

To update the American Society of Clinical Oncology (ASCO)/College of American Pathologists (CAP) guideline recommendations for human epidermal growth factor receptor 2 (HER2) testing in breast cancer to improve the accuracy of HER2 testing and its utility as a predictive marker in invasive breast cancer.

METHODS

ASCO/CAP convened an Update Committee that included coauthors of the 2007 guideline to conduct a systematic literature review and update recommendations for optimal HER2 testing.

RESULTS

The Update Committee identified criteria and areas requiring clarification to improve the accuracy of HER2 testing by immunohistochemistry (IHC) or in situ hybridization (ISH). The guideline was reviewed and approved by both organizations.

RECOMMENDATIONS

The Update Committee recommends that HER2 status (HER2 negative or positive) be determined in all patients with invasive (early stage or recurrence) breast cancer on the basis of one or more HER2 test results (negative, equivocal, or positive). Testing criteria define HER2-positive status when (on observing within an area of tumor that amounts to > 10% of contiguous and homogeneous tumor cells) there is evidence of protein overexpression (IHC) or gene amplification (HER2 copy number or HER2/CEP17 ratio by ISH based on counting at least 20 cells within the area). If results are equivocal (revised criteria), reflex testing should be performed using an alternative assay (IHC or ISH). Repeat testing should be considered if results seem discordant with other histopathologic findings. Laboratories should demonstrate high concordance with a validated HER2 test on a sufficiently large and representative set of specimens. Testing must be performed in a laboratory accredited by CAP or another accrediting entity. The Update Committee urges providers and health systems to cooperate to ensure the highest quality testing. This guideline was developed through a collaboration between the American Society of Clinical Oncology and the College of American Pathologists and has been published jointly by invitation and consent in both Journal of Clinical Oncology and the Archives of Pathology & Laboratory Medicine.

Chromogenic in situ hybridization compared with other approaches to evaluate HER2/neu status in breast carcinomas

Human epidermal growth factor receptor 2 (HER2) has been evaluated in breast cancer patients to identify those most likely to benefit from herceptin-targeted therapy. HER2 amplification, detected in 20-30% of invasive breast tumors, is associated with reduced survival and metastasis. The most frequently used technique for evaluating HER2 protein status as a routine procedure is immunohistochemistry (IHC). HER2 copy number alterations have also been evaluated by fluorescence in situ hybridization (FISH) in moderate immunoexpression (IHC 2+) cases. An alternative procedure to evaluate gene amplification is chromogenic in situ hybridization (CISH), which has some advantages over FISH, including the correlation between HER2 status and morphological features. Other methodologies have also been used, such as silver-enhanced in situ hybridization (SISH) and quantitative real-time RT-PCR, to determine the number of HER2 gene copies and expression, respectively. Here we will present a short and comprehensive review of the current advances concerning HER2 evaluation in human breast cancer.

Dual-colour chromogenic in-situ hybridization is a potential alternative to fluorescence in-situ hybridization in HER2 testing

AIM

Dual-colour chromogenic in-situ hybridization (dc-CISH) is an emerging methodology for characterizing genomic alterations. This study was aimed at evaluating the performance of a dc-CISH kit (ZytoVision) in determining human epidermal growth factor receptor 2 (HER2) status in breast cancer.

METHODS AND RESULTS

Two hundred and twenty-eight invasive breast carcinomas arranged in tissue microarrays were analysed in parallel with dc-CISH, fluorescence in-situ hybridization (FISH), and immunohistochemistry. Of 227 tumours with available FISH and dc-CISH results, HER2 amplification and non-amplification were detected in 49 (21.6%) and 178 (78.4%) tumours, respectively, by both assays. The concordance between dc-CISH and FISH results showed 100% agreement (κ-coefficient=1.00). Immunohistochemically, 162 (71%), 25 (11.0%) and 41 (18%) tumours were scored 0/1+, 2+, and 3+, respectively. The corresponding results with both FISH and dc-CISH demonstrated HER2 amplification in two (3.2%), nine (36%) and 38 (93%) tumours, respectively. Complete consensus among these three methods was observed in 197 cases, representing 98% of all 3+ and 0/1+ tumours (κ-coefficient=0.92). Confirmatory testing of 25 2+ tumours showed complete consensus between FISH and dc-CISH.

CONCLUSIONS

dc-CISH is a promising alternative to FISH in HER2 testing, and the single-institute incidence of HER2 amplification in breast cancer in Taiwan is 21.2%.

Clinical and health economic outcomes of alternative HER2 test strategies for guiding adjuvant trastuzumab therapy

AIM

To evaluate the clinical outcomes and cost-effectiveness of human epidermal growth factor receptor 2 (HER2) testing strategies to guide adjuvant trastuzumab (AT) therapy in women with HER2-positive breast cancer.

METHODS

A literature review produced 72 studies comparing HER2 test methods, and we computed concordance (assuming fluorescence in situ hybridization [FISH] as a reference assay) to assess performance relative to American Society of Clinical Oncology/College of American Pathologists (ASCO/CAP) guidelines. An economic analysis provided cost-effectiveness of alternative strategies, including a Monte Carlo simulation to vary key assumptions such as test price and performance.

RESULTS

Of 46 studies comparing immunohistochemistry (IHC) and FISH, only seven met the ASCO/CAP guideline of 95% or better concordance. A total of 14 out of 21 studies comparing chromogenic in situ hybridization and three out of five studies comparing silver-enhanced in situ hybridization met the guideline. Confirmation of IHC 2+ and 3+ and primary FISH strategies are likely to reduce costs and improve quality of life relative to confirmation of IHC 2+ only. Initial testing with a gene amplification-based assay is probably a cost-effective alternative to confirmation of IHC 2+ and 3+. The results are not sensitive to varying test price but are sensitive to test accuracy below 98%.

CONCLUSION

Using a primary gene amplification-based assay to guide AT therapy for HER2-positive breast cancer probably results in lower US medical costs, increased life-years and increased quality of life compared with confirmation of IHC 2+ with a gene amplification-based assay. We recommend the ASCO/CAP guidelines reflect 98% or greater concordance relative to a reference assay. Additional research regarding therapy response is required to further differentiate between gene amplification-based assays.

Update on HER2 testing for breast and upper gastrointestinal tract cancers

With the regulatory approvals in Europe and the USA of trastuzumab-based anti-HER2 targeted therapy for upper gastrointestinal cancers in 2010, HER2 testing has now become universal for newly diagnosed cases of both breast cancer and adenocarcinomas of esophagus, stomach and gastroesophageal origin. In the 12 years or more since the approval of trastuzumab for breast cancer, general refinements in approaches to HER2 testing, including a greater understanding of the implications of preanalytic factors impacting the test results and the application of standardization of reporting of HER2 test results, have taken place. There has also been continuing development in breast cancer with the introduction of new HER2 tests, including non-FISH tests, dimerization assays, phosphorylated HER2 receptor tests, mRNA-based tests, HER2 gene sequencing tests and the application of HER2 testing to circulating tumor cells. Most recently, the introduction of HER2 testing for upper gastrointentinal malignancies has emphasized the need for performing and interpreting slide-based assays in a manner unique to these specimens and not to apply the breast cancer testing protocols to esophageal and gastric adenocarcinomas.

Determination of HER2 amplification in primary breast cancer using dual-colour chromogenic in situ hybridization is comparable to fluorescence in situ hybridization: a European multicentre study involving 168 specimens

García-Caballero T, Grabau D, Green A R, Gregory J, Schad A, Kohlwes E, Ellis I O, Watts S & Mollerup J (2010) Histopathology56, 472–480 Determination of HER2 amplification in primary breast cancer using dual-colour chromogenic in situ hybridization is comparable to fluorescence in situ hybridization: a European multicentre study involving 168 specimens

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.

Visualization of FISH Probes by dual-color chromogenic in situ hybridization

The overall purpose of the study was to demonstrate applicability of the DAKO dual-color chromogenic in situ hybridization (CISH) assay (DAKO Denmark, Glostrup) with respect to 4 fluorescence in situ hybridization (FISH) probes: MYC (c-MYC), EGFR, ERBB2 (HER2), and TOP2A. The study showed that the dual-color CISH assay can convert Texas red and fluorescein isothiocyanate (FITC) signals into chromogenic signals with an almost complete 1:1 conversion ratio. Agreement studies between the FISH assays for HER2 and TOP2A and the corresponding CISH conversion assays showed 100% concordance (kappa values of 1.0) between the CISH and FISH methods for HER2 and TOP2A status. The correlations of the gene copy number to centromere-17 ratios were similarly high, with a correlation coefficient (r) for HER2 and TOP2A of more than 0.95. Owing to the relatively small number of specimens in this study, it is important that the data are confirmed in a larger study.

Emerging technologies for assessing HER2 amplification

Patients with human epidermal growth factor receptor-2 (HER2)+ breast cancer are eligible for trastuzumab treatment; therefore, accurate assessment of HER2 status is essential. Until recently, only 2 methods were validated for determining the HER2 status of breast tumors in the routine diagnostic setting: immunohistochemical analysis and fluorescence in situ hybridization (FISH). Recently, bright-field in situ hybridization techniques such as chromogenic in situ hybridization (CISH) and silver-enhanced in situ hybridization (SISH), which combine features of immunohistochemical analysis and FISH, have been introduced for the determination of HER2 status. These new techniques use a peroxidase enzyme-labeled probe with chromogenic detection, instead of a fluorescent-labeled probe, allowing results to be visualized by standard bright-field microscopy. Thus, the histologic features and HER2 status of a specimen can be evaluated in parallel. Moreover, signals do not decay over time. This review discusses recent publications regarding CISH and SISH testing, including results scoring and concordance between FISH and immunohistochemical analysis.

Performance of chromogenic in situ hybridization on testing HER2 Status in breast carcinomas with chromosome 17 polysomy and equivocal (2+) herceptest results: a study of two institutions using the conventional and new ASCO/CAP scoring criteria

This study specifically addressed the performance of chromogenic in situ hybridization (CISH) on HER2 testing in 66 breast carcinomas with chromosome 17 polysomy and 49 carcinomas with an equivocal HercepTest (DakoCytomation, Carpinteria, CA) score by comparing CISH with corresponding FISH results at 2 test sites and evaluating intersite agreement of CISH results. For tumors with chromosome 17 polysomy, when using the manufacturers' criteria, the concordance values between CISH and FISH at site A, site B, and intersite CISH agreement were 95.8%, 95.5%, and 93.5%, respectively; when using the American Society of Clinical Oncology/College of American Pathologists (ASCO/CAP) criteria, the values were 100.0%, 100.0%, and 100.0%, respectively. For tumors with an equivocal HercepTest score, when using the manufacturers' criteria, the concordance values between the 2 methods at site A, site B, and intersite CISH agreement were 88.2%, 95.1%, and 91.1%, respectively; when using the ASCO/CAP criteria, the values were 96.7%, 97.3%, and 97.4%, respectively. These results indicate that CISH is reliable for testing these 2 types of tumors, especially when the ASCO/CAP criteria are used.

The HER-2 receptor and breast cancer: ten years of targeted anti-HER-2 therapy and personalized medicine

The human epidermal growth factor receptor (HER-2) oncogene encodes a transmembrane tyrosine kinase receptor that has evolved as a major classifier of invasive breast cancer and target of therapy for the disease. The validation of the general prognostic significance of HER-2 gene amplification and protein overexpression in the absence of anti-HER-2 targeted therapy is discussed in a study of 107 published studies involving 39,730 patients, which produced an overall HER-2-positive rate of 22.2% and a mean relative risk for overall survival (OS) of 2.74. The issue of HER-2 status in primary versus metastatic breast cancer is considered along with a section on the features of metastatic HER-2-positive disease. The major marketed slide-based HER-2 testing approaches, immunohistochemistry, fluorescence in situ hybridization, and chromogenic in situ hybridization, are presented and contrasted in detail against the background of the published American Society of Clinical Oncology-College of American Pathologists guidelines for HER-2 testing. Testing issues, such as the impact of chromosome 17 polysomy and local versus central HER-2 testing, are also discussed. Emerging novel HER-2 testing techniques, including mRNA-based testing by real-time polymerase chain reaction and DNA microarray methods, HER-2 receptor dimerization, phosphorylated HER-2 receptors, and HER-2 status in circulating tumor cells, are also considered. A series of biomarkers potentially associated with resistance to trastuzumab is discussed with emphasis on the phosphatase and tensin homologue deleted on chromosome ten/Akt and insulin-like growth factor receptor pathways. The efficacy results for the more recently approved small molecule HER-1/HER-2 kinase inhibitor lapatinib are also presented along with a more limited review of markers of resistance for this agent. Additional topics in this section include combinations of both anti-HER-2 targeted therapies together as well as with novel agents including bevacizumab, everolimus, and tenespimycin. A series of novel HER-2-targeting agents is also presented, including pertuzumab, ertumaxomab, HER-2 vaccines, and recently discovered tyrosine kinase inhibitors. Biomarkers predictive of HER-2 targeted therapy toxicity are included, and the review concludes with a consideration of HER-2 status in the prediction of response to non-HER-2 targeted treatments including hormonal therapy, anthracyclines, and taxanes.

Quantitative real-time RT-PCR and chromogenic in situ hybridization: precise methods to detect HER-2 status in breast carcinoma

Background

HER-2 gene testing has become an integral part of breast cancer patient diagnosis. The most commonly used assay in the clinical setting for evaluating HER-2 status is immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH). These procedures permit correlation between HER-2 expression and morphological features. However, FISH signals are labile and fade over time, making post-revision of the tumor difficult. CISH (chromogenic in situ hybridization) is an alternative procedure, with certain advantages, although still limited as a diagnostic tool in breast carcinomas.

Methods

To elucidate the molecular profile of HER-2 status, mRNA and protein expression in 75 invasive breast carcinomas were analyzed by real time quantitative RT-PCR (qRT-PCR) and IHC, respectively. Amplifications were evaluated in 43 of these cases by CISH and in 11 by FISH.

Results

The concordance rate between IHC and qRT-PCR results was 78.9%, and 94.6% for qRT-PCR and CISH. Intratumoral heterogeneity of HER-2 status was identified in three cases by CISH. The results of the three procedures were compared and showed a concordance rate of 83.8%; higher discordances were observed in 0 or 1+ immunostaining cases, which showed high-level amplification (15.4%) and HER-2 transcript overexpression (20%). Moreover, 2+ immunostaining cases presented nonamplified status (50%) by CISH and HER-2 downexpression (38.5%) by qRT-PCR. In general, concordance occurred between qRT-PCR and CISH results. A high concordance was observed between CISH/qRT-PCR and FISH. Comparisons with clinicopathological data revealed a significant association between HER-2 downexpression and the involvement of less than four lymph nodes (P = 0.0350).

Conclusion

Based on these findings, qRT-PCR was more precise and reproducible than IHC. Furthermore, CISH was revealed as an alternative and useful procedure for investigating amplifications involving the HER-2 gene.

Salivary duct carcinoma in situ of the parotid gland

AIMS

To describe three cases of purely in situ salivary duct carcinoma, so as better to define the entity.

METHODS AND RESULTS

Three primary tumours of the parotid gland are presented, in each case composed of cysts and ducts and lined by high nuclear grade epithelial cells. All parts of each tumour were surrounded by a myoepithelial cell rim and there was no evidence of invasion. The tumour cells expressed immunohistochemical markers seen in invasive salivary duct carcinoma of usual (high-grade) type. In two cases the androgen receptor (AR) reaction was strong, but there was no immunohistochemical expression of HER2 protein or gene amplification by in situ hybridization. In the remaining case, fewer nuclei stained for AR, but both HER2 protein and gene amplification were demonstrated.

CONCLUSIONS

Salivary duct carcinoma in situ is morphologically similar to breast ductal carcinoma in situ and, although our cases are few, salivary duct carcinoma in situ can possibly be subdivided into luminal and non-luminal cell types, as can analogous mammary neoplasms. The present study cannot determine whether low-grade cribriform cystadenocarcinoma, architecturally similar but immunohistochemically different, is part of the spectrum of salivary duct carcinoma in situ, or whether it represents a separate entity.

Delineation of HER2 gene status in breast carcinoma by silver in situ hybridization is reproducible among laboratories and pathologists

An automated enzyme metallographic silver in situ hybridization method (SISH) has been reported to successfully determine human epidermal growth factor receptor 2 (HER2) gene amplification. We evaluated the staining and interpretative reproducibility of the HER2 SISH assay at five laboratories and compared SISH results with other in situ hybridization (ISH) methods. The HER2 gene status of 89 breast carcinomas was analyzed in parallel using manual dual-color fluorescence ISH, manual chromogenic ISH, and bright-field automated SISH. A total of 1098 SISH-stained slides were evaluated. For comparison, all specimens were stained by 4B5 immunohistochemistry for HER2 protein expression. Interpretation was performed by pathologists at five different laboratories using the algorithms provided by the manufacturers and the guidelines of American Society of Clinical Oncology/College of American Pathologists. Staining and interpretative reproducibility were measured through the computation of weighted kappa statistics. Following the optimization of SISH staining, 1077/1098 (98%) of slides were evaluable. Excellent reproducibility and efficacy of HER2 SISH staining, and interobserver interpretation (Kw = 0.91), were observed among five sites. For the 89 invasive breast cancer cases, the overall rate of concordance between consensus 4B5 and consensus SISH, fluorescence ISH, and chromogenic ISH was 96.6% (86/89), 97.8% (87/89), and 96.6% (86/89), respectively. Overall concordance between positive and negative SISH and fluorescence ISH results, as well as between individual and consensus positive and negative SISH results, was excellent (P < 0.001).