Co-amplification of the HER2 gene and chromosome 17 centromere: a potential diagnostic pitfall in HER2 testing in breast cancer

Atypical Co-amplification with Co-localization of HER2 Gene in Breast Cancer: Combined IHC/FISH Approach as per ASCO/CAP 2018 Guidelines for Targeted Therapy Eligibility

Breast cancer patients with HER2 gene amplification as assessed by FISH are eligible for HER2-targeted therapy. However, in a small subset of patients, unusual FISH pattern of co-localization and co-amplification can pose challenges in interpretation of the HER2 status and hence to assess the HER2 status accurately; our aim was to report their incidence and analyze them based on latest ASCO/CAP 2018 guidelines. We present seven cases with HER2/CEP17 co-amplification and co-localization from a total 4040 cases referred during the year 2017 to 2021 at Mumbai Reference Laboratory, SRL Diagnostics. Core needle biopsy/excision invasive breast carcinoma specimens from metastatic sites were tested for IHC for expressions of ER, PR, and HER2. The ones which came equivocal on HER2 IHC were then evaluated for HER2 amplification by FISH. Co-amplification and co-localization of HER2 and centromeric 17 was observed with a frequency of 0.1% that falls in the range of 0.5-0.1% as reported from other large-scale studies. Our study showed that implementation of a binary inhouse concurrent assessment with IHC as per the ASCO/CAP 2018 helps to reach the most definitive and accurate HER2 status. Our study is an attempt to report such challenging FISH patterns and their work-up for a better understanding on the interpretation. Cumulative data along with follow-up in these cases would bring an insight into exact therapeutic outcome.

Loss of HER2 in breast cancer: biological mechanisms and technical pitfalls

Loss of HER2 in previously HER2-positive breast tumors is not rare, occurring in up to 50% of breast cancers; however, clinical research and practice underestimate this issue. Many studies have reported the loss of HER2 after neoadjuvant therapy and at metastatic relapse and identified clinicopathological variables more frequently associated with this event. Nevertheless, the biological mechanisms underlying HER2 loss are still poorly understood. HER2 downregulation, intratumoral heterogeneity, clonal selection, and true subtype switch have been suggested as potential causes of HER2 loss, but translational studies specifically investigating the biology behind HER2 loss are virtually absent. On the other side, technical pitfalls may justify HER2 loss in some of these samples. The best treatment strategy for patients with HER2 loss is currently unknown. Considering the prevalence of this phenomenon and its apparent correlation with worse outcomes, we believe that correlative studies specifically addressing HER2 loss are warranted.

[2021 update of the GEFPICS' recommendations for HER2 status assessment in invasive breast cancer in France]

The last international guidelines on HER2 determination in breast cancer have been updated in 2018 by the American Society of Clinical Oncology and College of American Pathologists, on the basis of a twenty-year practice and results of numerous clinical trials. Moreover, the emerging HER2-low concept for 1+ and 2+ non amplified breast cancers lead to refine French practices for HER2 status assessment. The GEFPICS group, composed of expert pathologists, herein presents the latest French recommendations for HER2 status evaluation in breast cancer, taking into account the ASCO/CAP guidelines and introducing the HER2-low concept. In the era of personalized medicine, HER2 status assessment remains one of the most important biomarkers in breast cancer and its quality guaranties the optimal patients' care. French pathologists' commitment in theranostic biomarker quality is more than ever required to provide the most efficient cares in oncology.

Genome oligopaint via local denaturation fluorescence in situ hybridization

Cas9 in complex with a programmable guide RNA targets specific double-stranded DNA for cleavage. By harnessing Cas9 as a programmable loader of superhelicase to genomic DNA, we report a physiological-temperature DNA fluorescence in situ hybridization (FISH) method termed genome oligopaint via local denaturation (GOLD) FISH. Instead of global denaturation as in conventional DNA FISH, loading a superhelicase at a Cas9-generated nick allows for local DNA denaturation, reducing nonspecific binding of probes and avoiding harsh treatments such as heat denaturation. GOLD FISH relies on Cas9 cleaving target DNA sequences and avoids the high nuclear background associated with other genome labeling methods that rely on Cas9 binding. The excellent signal brightness and specificity enable us to image nonrepetitive genomic DNA loci and analyze the conformational differences between active and inactive X chromosomes. Finally, GOLD FISH could be used for rapid identification of HER2 gene amplification in patient tissue.

Impact of chromosome 17 centromere copy number increase on patient survival and human epidermal growth factor receptor 2 expression in gastric adenocarcinoma

The accurate evaluation of human epidermal growth factor receptor 2 (HER2) status is essential for the appropriate use of targeted therapies. An increased number of chromosome 17 centromere enumeration probe (CEP17) signals may underrate fluorescence in situ hybridization (FISH) outcomes, resulting in false-negative or a false-equivocal HER2 status assessment. The aim of the present study was to assess the frequency of CEP17 copy number increase (CNI), its effects on HER2 protein expression (and the subsequent effects on tumor cells), and the survival outcomes of patients with gastric cancer. Archival primary tumor samples from 244 patients that underwent gastric resection for adenocarcinoma were retrieved for both HER2 protein expression analysis (using immunochemistry) and HER2 gene amplification (using FISH). The associations between HER2 status, CEP17 CNI and multiple clinicopathological parameters (including survival outcome), were assessed. The relationship between CEP17 CNI and HER2 protein upregulation was also investigated. CEP17 CNI was detected in 17.2% of cases, and a strong association between CEP17 CNI and HER2 upregulation was revealed. The impact of CEP17 CNI on survival did not reach statistical significance. Consequently, CEP17 CNI was discovered to be strongly associated with HER2 upregulation in tumor cells, which may characterize a critical issue in HER2 testing. Therefore, the eligibility for HER2-targeted agents in CEP17 CNI-positive patients warrants further recognition.

Next-generation assessment of human epidermal growth factor receptor 2 gene (ERBB2) amplification status in invasive breast carcinoma: a focus on Group 4 by use of the 2018 American Society of Clinical Oncology/College of American Pathologists HER2 testing guideline

AIMS

The American Society of Clinical Oncology/College of American Pathologists (ASCO/CAP) updated the testing guideline in 2018 to address issues arising from uncommon human epidermal growth factor receptor 2 (HER2) fluorescence in-situ hybridisation (FISH) results according to the 2013 guideline. Next-generation sequencing (NGS) may be used to better classify patients. The aim of this study was to assess the ERBB2 amplification status of invasive breast carcinoma with equivocal HER2 immunohistochemistry (IHC) results by using NGS, focusing on Group 4 (HER2/CEP17 ratio of <2.0; average HER2 signals/cell of ≥4.0 and <6.0).

METHODS AND RESULTS

We retrospectively reviewed HER2 FISH and NGS data of HER2 IHC-equivocal breast carcinomas at our centre between January 2009 and September 2019, wherein all three assays were performed on the same tissue block, and compared HER2 FISH results, according to the 2018 ASCO/CAP guideline, and the ERBB2 amplification status determined with NGS. A total of 52 HER2 FISH and NGS results from 51 patients with HER2 IHC-equivocal breast carcinomas were reviewed. The cohort included eight cases classified as 2018 ASCO/CAP in-situ hybridisation Group 1, three classified as Group 2, three classified as Group 3, 14 classified as Group 4, and 24 classified as Group 5. Thirteen of 14 (92.9%) Group 4 (HER2-negative) cases were classified as ERBB2-non-amplified by the use of NGS; the discordant case was later classified as Group 1 with alternative sample FISH testing. NGS revealed no significant difference in somatic mutations or copy number alterations between Groups 4 and 5.

CONCLUSIONS

Our NGS findings support the reclassification of HER2 FISH-equivocal cases as HER2-negative under the 2018 ASCO/CAP guideline.

Evolving concepts in HER2 evaluation in breast cancer: Heterogeneity, HER2-low carcinomas and beyond

The human epidermal growth factor receptor 2 (HER2) is a well-known negative prognostic factor in breast cancer and a target of the monoclonal antibody trastuzumab as well as of other anti-HER2 compounds. Pioneering works on HER2-positive breast cancer in the 90s' launched a new era in clinical research and oncology practice that has reshaped the natural history of this disease. In diagnostic pathology the HER2 status is routinely assessed by using a combination of immunohistochemistry (IHC, to evaluate HER2 protein expression levels) and in situ hybridization (ISH, to assess HER2 gene status). For this purpose, international recommendations have been developed by a consensus of experts in the field, which have changed over the years according to new experimental and clinical data. In this review article we will document the changes that have contributed to a better evaluation of the HER2 status in clinical practice, furthermore we will discuss HER2 heterogeneity defined by IHC and ISH as well as by transcriptomic analysis and we will critically describe the complexity of HER2 equivocal results. Finally, we will introduce the clinical impact of HER2 mutations and we will define the upcoming category of HER2-low breast cancer with respect to emerging clinical data on the efficacy of specific anti-HER2 agents in subgroups of breast carcinomas lacking the classical oncogene addition dictated by HER2 amplification.

HER2, chromosome 17 polysomy and DNA ploidy status in breast cancer; a translational study

Breast cancer treatment depends on human epidermal growth factor receptor-2 (HER2) status, which is often determined using dual probe fluorescence in situ hybridisation (FISH). Hereby, also loss and gain of the centromere of chromosome 17 (CEP17) can be observed (HER2 is located on chromosome 17). CEP17 gain can lead to difficulty in interpretation of HER2 status, since this might represent true polysomy. With this study we investigated whether isolated polysomy is present and how this effects HER2 status in six breast cancer cell lines and 97 breast cancer cases, using HER2 FISH and immunohistochemistry, DNA ploidy assessment and multiplex ligation dependent probe amplification. We observed no isolated polysomy of chromosome 17 in any cell line. However, FISH analysis did show CEP17 gain in five of six cell lines, which reflected gains of the whole chromosome in metaphase spreads and aneuploidy with gain of multiple chromosomes in all these cases. In patients' samples, gain of CEP17 indeed correlated with aneuploidy of the tumour (91.1%; p < 0.001). Our results indicate that CEP17 gain is not due to isolated polysomy, but rather due to widespread aneuploidy with gain of multiple chromosomes. As aneuploidy is associated with poor clinical outcome, irrespective of tumour grade, this could improve future therapeutic decision making.

Immunohistochemistry and alternative FISH testing in breast cancer with HER2 equivocal amplification

Purpose

While HER2 testing is well established in directing appropriate treatment for breast cancer, a small percentage of cases show equivocal results by immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH). Alternative probes may be used in equivocal cases. We present a single community-based institution’s experience in further evaluating these cases.

Patients and methods

Between 2014 and 2016, 4255 samples were submitted for HER2 amplification testing by alternative probes, TP53, RAI1, and RARA. Of the patients tested by FISH, 505/3908 (12.9%) also had IHC data.

Results

Most (73.9%) FISH equivocal cases remained equivocal after IHC testing. However, 50.5% of equivocal cases were classified as HER2 amplified by alternative probes. Most cases were positive by more than one probe: 78% of positive cases by RAI1 and 73.9% by TP53. There was a significant difference between IHC and FISH alternative testing (p < 0.0001) among the equivocal cases by conventional FISH testing, 44% of IHC negative cases became positive while 36% of the positive IHC cases became negative by alternative FISH testing. Available data showed that 41% of patients were treated with palbociclib and were positive by alternative FISH.

Conclusion

The prevalence of double HER2 equivocal cases and the discrepancy between IHC and alternative FISH testing suggest that FISH alternative testing using both RAI1 and TP53 probes is necessary for conclusive classification. Because almost half of FISH equivocal cases converted to HER2 amplified upon alternative testing, clinical studies to determine the benefit of anti-HER2 therapy in these patients are urgently needed.

Retrospective analysis of the association between human epidermal growth factor receptor 2 amplification and chromosome enumeration probe 17 status in patients with breast cancer

The aim of the present study was to identify potential human epidermal growth factor receptor 2 (HER2) amplification, according to American Society of Clinical Oncology and the College of American Pathologists (ASCO/CAP) 2013 HER2 testing guidelines, in patients previously determined not to possess HER2 amplification, in accordance with previous 2007 guidelines. Potential discrepancies may arise from chromosome enumeration probe 17 (CEP17) amplification, deletion, polysomyor monosomy. HER2, CEP17, tumor protein p53 (TP53) and retinoic acid receptor α (RARA) genes from 67 patient specimens with suspected amplification, polysomy or monosomy of CEP17 were analyzed using fluorescence in situ hybridization. HER2 status was interpreted using 2007 and 2013 ASCO HER2 test guidelines as well as the reference genes TP53 and RARA. According to ASCO/CAP2007 HER2 guidelines, 20 patients exhibited HER2 amplification (29.85%), 41 were without HER2 amplification (including 25 with polysomy, 15 with monosomy and 1 with suspected monosomy plus co-amplification of HER2 and CEP17) and the remaining 6 patients were equivocal. Using ASCO/CAP 2013 HER2 guidelines, 49 patients exhibited HER2 gene amplification (73.1%). The 29-patient increase included 6 originally at equivocal levels but now demonstrating amplification, 22 originally with polysomy but now revealing co-amplification, and 1 with suspected monosomy plus co-amplification of HER2 and CEP17. According to TP53 and RARA, HER2 was amplified in 43 patients (64.1%). Using the revised guidelines, HER2, originally identified as amplified in 6 patients, was not amplified following the introduction of TP53 and RARA control genes. Among these 6, 4 possessed normal TP53 and RARA. The incidence of co-amplification of HER2 and CEP17 was 1.4% (21/1,518). RARA and TP53 are suitable control genes to evaluate HER2 status.

TOP2A, GGH, and PECAM1 are associated with hematogenous, lymph node, and peritoneal recurrence in stage II/III gastric cancer patients enrolled in the ACTS-GC study

Background

To identify factors related to relapse sites, we carried out an exploratory biomarker analysis of data from the Adjuvant Chemotherapy Trial of TS-1 for Gastric Cancer study, which is a randomized, controlled trial comparing postoperative adjuvant S-1 therapy with surgery alone in 1,059 patients with stage II/III gastric cancer.

Patients and Methods

Surgical specimens from 829 patients were retrospectively examined, and 63 genes involved in a variety of biological processes were analyzed by quantitative real-time PCR. Gene expression normalized to reference genes was categorized as lower or higher than the median, and association with relapse sites was analyzed based on 5-year relapse-free survival.

Results

Hematogenous, lymph node, and peritoneal recurrence developed in 72, 105, and 138 of the 829 patients, respectively; hazard ratios were 0.79 (95% confidential interval: 0.54–1.16), 0.51 (0.31–0.82), and 0.60 (0.42–0.84), respectively. Expression of platelet/endothelial cell adhesion molecule 1 (PECAM1) and topoisomerase II alpha (TOP2A) was strongly correlated with hematogenous recurrence and peritoneal recurrence, respectively (false discovery rate = 7.7×10⁻⁵ and 0.002, respectively). Gamma-glutamyl hydrolase (GGH) expression was moderately correlated with lymph node recurrence (false discovery rate = 0.34). Relapse-free survival was worse in patients expressing high levels of PECAM1 (hazard ratio = 2.37, 1.65–3.41), TOP2A (hazard ratio = 2.35, 1.55–3.57), or GGH (hazard ratio = 1.87, 1.13–3.08), respectively. A multivariate analysis revealed that these were stronger independent risk factors than tumor histological type.

Conclusion

In patients with stage II/III gastric cancer, TOP2A, GGH, and PECAM1 levels in primary tumors are linked to high risk of hematogenous, lymph node, and peritoneal recurrence, respectively.

RAI1 Alternate Probe Identifies Additional Breast Cancer Cases as Amplified Following Equivocal HER2 Fluorescence In Situ Hybridization Testing: Experience From a National Reference Laboratory

Context.—In 2013 the American Society of Clinical Oncology and College of American Pathologists updated the HER2 guidelines and changed the equivocal category for HER2 in situ hybridization testing to an average HER2 copy number of 4.0 to 5.9 with a HER2:CEP17 ratio of less than 2.0 and proposed retesting, with an option of using another control probe to avoid false-negative results. RAI1, located at band position 17p11.2, is a popular alternate probe locus for retesting equivocal changes.

Objective.—To review experience with the RAI1 alternate probe in HER2 fluorescence in situ hybridization equivocal breast cancers.

Design.—Primary and metastatic breast cancers with equivocal HER2 fluorescence in situ hybridization, retested with an alternate (RAI1) probe, were identified. HER2, RAI1, and CEP17 copy numbers, HER2 to control probe ratios, and genetic heterogeneity were recorded. Hematoxylin-eosin–stained slides were reviewed for type and grade of cancer.

Results.—Of 876 cases tested with CEP17 as the reference probe, 97 (11.1%) had equivocal HER2 fluorescence in situ hybridization results. Additional testing with the RAI1 probe classified 39.2% cases (38 of 97) as amplified with a HER2:RAI1 ratio ranging from 2.0 to 3.2 (mean, 2.37); 3.1% (3 of 97) were still unclassifiable because of a deletion of RAI1.

Conclusions.—RAI1 identified close to 40% of original HER2 fluorescence in situ hybridization equivocal cases as amplified, making these patients eligible for targeted therapies. It is not known whether guidelines for US Food and Drug Administration–approved probes can be extrapolated to alternate probes when an alternate control probe shows losses or gains. Because of the lack of guidelines for reporting HER2 status with alternate probes, laboratories face challenges in interpreting results.

Prognostic significance of equivocal human epidermal growth factor receptor 2 results and clinical utility of alternative chromosome 17 genes in patients with invasive breast cancer: A cohort study

BACKGROUND

The 2013 testing guidelines for determining the human epidermal growth factor receptor 2 (HER2) status include new cutoff points for the HER2/chromosome enumeration probe 17 (CEP17) ratio and the average HER2 copy number per cell, and they recommend using a reflex test with alternative chromosome 17 probes (Ch17Ps) to resolve equivocal HER2 results. This study sought to determine the clinical utility of alternative Ch17Ps in equivocal cases and the effects of equivocal results and/or a change in the HER2 status on patients' outcomes.

METHODS

The University of Texas MD Anderson Cancer Center database of HER2 dual-probe fluorescence in situ hybridization results from 2000 to 2010 was searched for cases of invasive breast cancer with HER2/CEP17 ratios < 2 and average HER2 copy numbers < 6 per cell. Cases with HER2 copy numbers of 4 to < 6 (the definition of equivocal HER2 results) were analyzed with alternative Ch17Ps for Smith-Magenis syndrome and retinoic acid receptor α genes. Disease-free survival (DFS) and overall survival (OS) were evaluated with respect to the HER2 copy number with multivariate Cox proportional hazards regression.

RESULTS

Among the 3630 patients meeting the inclusion criteria, 137 (4%) had equivocal HER2 results. With alternative Ch17Ps, 35 of 57 equivocal HER2 cases (61%) were upgraded to a positive HER2 status, and 22 cases (39%) remained unchanged. The 5-year DFS and OS adjusted hazard ratios (HRs) for copy numbers of 4 to < 6 versus < 4 were 0.6 (95% confidence interval [CI], 0.3-1.2) and 0.5 (95% CI, 0.2-1.0) with P values of .16 and .66, respectively. In comparison with HER2-negative cases, these CIs indicated that equivocal HER2 results were associated with either a protective effect (HR, < 0.5) or no effect (HR, 1.0).

CONCLUSIONS

These findings rule out a significant deleterious effect of equivocal HER2 results. Alternative Ch17Ps may erroneously upgrade the HER2 status; therefore, they cannot be considered reliable in clinical practice. Cancer 2017;123:1115-1123. © 2016 American Cancer Society.

Cytogenetic and immunohistochemical biomarker profiling of therapy-relevant factors in salivary gland carcinomas

OBJECTIVES

There is currently no established algorithm for the molecular profiling of therapy-relevant defects in salivary gland carcinomas (SGC). HER2 overexpression in a subfraction of SGC and low frequencies of EGFR mutations are known. Here, we established receptor and cell signalling profiles of 17 therapy-relevant factors and propose a molecular diagnostic algorithm for SGC.

MATERIALS AND METHODS

Formalin-fixed and paraffin-embedded tissue samples from SGC (n = 38) were analysed with immunohistochemistry and fluorescence in situ hybridisation (FISH).

RESULTS

Two or more expressed receptors and/or receptor gene amplification were detectable in eight of 38 (21%) tumours: HER2 3+/AR 1+, HER3 gene amplification/AR 1+/EGFR 1+, ER 3+/AR 1+, EGFR 2+/PR 1+ and EGFR 2+/PR 1+/AR 1+. No FGFR1-3, MET, ALK1, ROS1, RET, BRAF nor VEGFA defects were detectable, and ERCC1 was not overexpressed. No PD1+ tumour-infiltrating T cells were detectable.

CONCLUSION

Personalised therapy of patients with salivary gland carcinomas should include HER2 and EGFR signalling testing and, in negative cases, evaluation of rare potential target molecules. ERCC1 and PD1 do not appear to be reliable markers for the decision for or against chemotherapy or immunotherapy, respectively.

The FlexISH assay brings flexibility to cytogenetic HER2 testing

AIMS

Fluorescence in-situ hybridization (FISH) is the method of choice for quantitative human epidermal growth factor receptor 2 (HER2) (also known as ERBB2) gene testing in invasive breast cancer. HER2 testing has great clinical impact, and is often claimed to expeditiously complete the entire diagnostic procedure for an individual patient. Against this background, the aim of this study was to evaluate the usefulness and performance of a novel dual-colour HER2/cen17 FISH assay designed to facilitate flexible (overnight) and rapid (<2 h of hybridization) FISH.

METHODS AND RESULTS

We quantitatively and qualitatively compared counting results and the performance of the FlexISH SPEC ERBB2/CEN 17 dual-colour hybridization kit with well-established HER2FISH assays, by using 90 malignant (polysomic and non-polysomic) and 19 benign paraffin-embedded breast tissue specimens. We used long (overnight) and short (2 h) hybridization periods, and found an excellent correlation between the FISH results obtained with FlexISH, ZytoLight and PathVysion hybridization probes.

CONCLUSIONS

The results obtained with both the short-run and long-run application of FlexISH are in excellent accordance with the results obtained with other commercially available FISH kits. This appears to be true in all relevant respects: signal counts, signal-to-noise ratio, brightness, and distinctness of HER2 and cen17 signals. As FlexISH probes can be equivalently used as a short-run or long-run application, the FlexISH probe kit provides the highest flexibility in terms of time and laboratory management. If required, a reliable HER2 finding can be delivered within 4.5 h, but the standard workflow (including overnight hybridization) does not negatively affect the performance, specimen quality or diagnostic result.

Frequency of chromosome 17 polysomy in relation to CEP17 copy number in a large breast cancer cohort

Eligibility to anti-HER2 therapy for breast tumors strictly depends on demonstrating HER2 overexpression (by immunohistochemistry) or HER2 gene amplification by in situ hybridization (ISH), usually defined by the ratio of HER2 gene to chromosome 17 centromere (CEP17) copies. However, the CEP17 copy number increase (CNI) has been proven responsible for misleading HER2 FISH results and recent small cohort studies suggest that chromosome 17 polysomy is actually very rare. Here we investigated by FISH the frequency of true chromosome 17 polysomy in a consecutive cohort of 5,477 invasive breast cancer patients. We evaluated and selected the LSI 17p11.2 probe for chromosome 17 enumeration on a training cohort of 67 breast cancer samples (CEP17 ≥ 2.5). LSI 17p11.2 was used in the 297/5,477 patients from the validation cohort displaying CEP17 CNI (CEP17 ≥ 3.0). Using HER2/17p11.2 scoring criteria, 37.3%/1.5% patients initially classified as equivocal/non-amplified were reclassified as amplified. For a more accurate assessment of chromosome 17 and ploidy in the samples, we tested six markers located on chromosome 17 and centromeric regions of chromosome 8 (CEP8) and 11 (CEP11) in 67 patients with CEP17 and LSI 17p11.2 CNI. True polysomy (hyperdiploidy) according to these markers was found in 0.48% of cases (24/5,020). CEP8 and CEP11 CNI (≥3.0) was more frequent in the hyperdiploid than CEP17 non-polysomic group (55.6% vs. 6.1% and 25% vs. 2.3%, respectively). Our results suggest that chromosome 17 polysomy is a rare event found in <1% breast cancer cases and that polysomy of other chromosomes frequently occurs with chromosome 17 polysomy.

Application of the 2013 ASCO/CAP guideline and the SISH technique for HER2 testing of breast cancer selects more patients for anti-HER2 treatment

The aim of this study is to assess the impact of changes of the 2013 ASCO/CAP guideline on the results of HER2 testing in breast cancer. A series of 916 primary invasive breast cancer cases, assessed as HER2 2+ by IHC in part using the 2007 and in part the 2013 ASCO/CAP criteria, was evaluated for HER2 amplification status by SISH and classified according to both 2007 and 2013 ASCO/CAP ISH guideline criteria. We observed a significant increase of HER2-positive cases (12.4 to 16.8%) and a decrease of HER2-equivocal cases (3.6 to 0.7%). Of the cases studied, 52.1% fulfilled both criteria of HER2/CEP17 ratio and average HER2 copy number per cell to be classified as HER2-positive. Reclassification of the cases from before the introduction of the new ASCO/CAP guideline with the 2013 ISH criteria resulted in an increase of cases with a HER2-positive status (12.4 to 14.2%) and in a decrease of HER2-equivocal cases (3.6 to 1.6%). The 2013 ASCO/CAP guideline selects more patients for anti-HER2 targeted therapy, mostly based on the modifications of criteria to evaluate ISH-HER2.

A meta-analysis on concordance between immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH) to detect HER2 gene overexpression in breast cancer

BACKGROUND

We performed this meta-analysis study to evaluate the concordance and discordance between immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH) in detecting HER2 alteration in human breast cancer.

METHODS

As a meta-analysis, the present study evaluated the available data from previous studies on the HER2 gene detected by IHC and FISH. To indicate the meta-analysis results, a forest plot was used.

RESULTS

We identified 172 citations, for which our inclusion criteria were met by 18 articles, representing 6629 cases. The overall concordance and discordance rate between IHC staining with score 0/1+ and FISH for detection failure of HER2 expression was 96 and 4 %, respectively. The present study showed that the overall proportion of FISH positive and negative rate for IHC score 2+ for detection of HER2 expression was 36 and 64 %, respectively; and 91 and 9 % for 3+ IHC scores.

CONCLUSION

The results of this study show that IHC score 0/1+ and 3+ cannot be completely considered as negative and positive breast cancer test, respectively. Therefore, we suggest a valid and complementary test, the same as FISH, to explore HER2 expression.

Brain metastases in gastro-oesophageal adenocarcinoma: insights into the role of the human epidermal growth factor receptor 2 (HER2)

Background:

Gastro-oesophageal adenocarcinomas rarely metastasize to the central nervous system (CNS). The role of the human epidermal growth factor receptor 2 (HER2) in patients with these cancers and CNS involvement is presently unknown.

Patients and Methods:

A multicentre registry was established to collect data from patients with gastro-oesophageal adenocarcinomas and CNS involvement both retrospectively and prospectively. Inclusion in the study required a predefined clinical data set, a central neuro-radiological or histopathological confirmation of metastatic CNS involvement and central assessment of HER2 by immunohistochemistry (IHC) and in situ hybridisation (ISH). In addition, expression of E-cadherin and DNA mismatch repair (MMR) proteins were assessed by IHC.

Results:

One hundred patients fulfilled the inclusion criteria. The population's median age was 59 years (interquartile range: 54–68), of which 85 (85%) were male. Twenty-five patients were of Asian and 75 of Caucasian origin. HER2 status was positive in 36% (95% CI: 26.6–46.2) of cases. Median time from initial diagnosis to the development of brain metastases (BMets) or leptomeningeal carcinomatosis (LC) was 9.9 months (95% CI: 8.5–15.0). Median overall survival from diagnosis was 16.9 months (95% CI: 14.0–20.7) and was not related to the HER2 status. E-cadherin loss was observed in 9% of cases and loss of expression in at least one DNA MMR proteins in 6%.

Conclusions:

The proportion of a positive HER2 status in patients with gastro-oesophageal adenocarcinoma and CNS involvement was higher than expected. The impact of anti-HER2 therapies should be studied prospectively.

Advances in the Molecular Analysis of Breast Cancer: Pathway toward Personalized Medicine

Background

Breast cancer is a heterogeneous disease that encompasses a wide range of clinical behaviors and histological and molecular variants. It is the most common type of cancer affecting women worldwide and is the second leading cause of cancer death.

Methods

A comprehensive literature search was performed to explore the advances in molecular medicine related to the diagnosis and treatment of breast cancer.

Results

During the last few decades, advances in molecular medicine have changed the landscape of cancer treatment as new molecular tests complement and, in many instances, exceed traditional methods for determining patient prognosis and response to treatment options. Personalized medicine is becoming the standard of care around the world. Developments in molecular profiling, genomic analysis, and the discovery of targeted drug therapies have significantly improved patient survival rates and quality of life.

Conclusions

This review highlights what pathologists need to know about current molecular tests for classification and prognostic/predictive assessment of breast carcinoma as well as their role as part of the medical team.

Gene status in HER2 equivocal breast carcinomas: impact of distinct recommendations and contribution of a polymerase chain reaction-based method

BACKGROUND

The primary objectives of this study on carcinomas with equivocal HER2 expression were to assess the impact of distinct recommendations with regard to identifying patients eligible for anti-HER2 agents by fluorescence in situ hybridization (FISH) and to elucidate whether multiplex ligation-dependent probe amplification (MLPA) may be of support in assessing HER2 gene status.

METHODS

A cohort of 957 immunohistochemistry-evaluated HER2-equivocal cases was analyzed by dual-color FISH. The results were assessed according to U.S. Food and Drug Administration (FDA) and European Medicines Agency (EMA) guidelines and American Society of Clinical Oncology (ASCO) and College of American Pathologists (CAP) 2007 and 2013 guidelines for dual- and single-signal in situ hybridization (ISH) assays. A subgroup of 112 cases was subjected to MLPA.

RESULTS

HER2 amplification varied from 15% (ASCO/CAP 2007 HER2/CEP17 ratio) to 29.5% (FDA/EMA HER2 copy number). According to the ASCO/CAP 2013 interpretation of the dual-signal HER2 assay, ISH-positive carcinomas accounted for 19.7%. In contrast with the ASCO/CAP 2007 ratio, this approach labeled as positive all 32 cases (3.34%) with a HER2/CEP17 ratio <2 and an average HER2 copy number ≥6.0 signals per cell. In contrast, only one case showing a HER2 copy number <4 but a ratio ≥2 was diagnosed as positive. MLPA data correlated poorly with FISH results because of the presence of heterogeneous HER2 amplification in 33.9% of all amplified carcinomas; however, MLPA ruled out HER2 amplification in 75% of ISH-evaluated HER2-equivocal carcinomas.

CONCLUSION

The ASCO/CAP 2013 guidelines seem to improve the identification of HER2-positive carcinomas. Polymerase chain reaction-based methods such as MLPA can be of help, provided that heterogeneous amplification has been ruled out by ISH.

Assessment of HER2 status in breast cancer: overall positivity rate and accuracy by fluorescence in situ hybridization and immunohistochemistry in a single institution over 12 years: a quality control study

Background

The gold standard of HER2 status assessment in breast cancer is still debated. Immunohistochemistry (IHC) and in-situ technology as fluorescent-labeled methodology (FISH) can be influenced by pre-analytical factors, assay-conditions and interpretation of test results. We retrospectively conducted this quality control study and analyzed HER2 test results in breast cancer within the routine diagnostic service in a single institution over a period of 12 years. We addressed the question how stable and concordant IHC and FISH methods are and whether HER2 positivity rate has changed over this period.

Methods

Data of 7714 consecutive HER2-FISH-assays in a period of 12 years (2001–2012) on breast cancer biopsies and excision specimens were retrospectively analyzed. From 2001 to 2004, FISH tests were performed from all cases with IHC score 3+ and 2+ (and in some tumors with IHC score 1+ and 0). From 2005–2010, HER2 status was only determined by FISH. From 2011–2012, all breast carcinomas were analyzed by both IHC and FISH. Scoring and cut-off-definition were done according to time-current ASCO-CAP and FDA-guidelines.

Results

Between 2001–2004, IHC score 3+ was diagnosed in 22% of cases, 69% of these 3+ cases were amplified by FISH. 6% of IHC score 0/1+ cases were amplified by FISH. There was a mean amplification rate of 15.8% (range 13 -19%) using FISH only HER2-assays (2005–2010). Starting 2008, a slight drop in the amplification rate from 17% to 14% was noticed due to the modified ASCO-criteria in 2007. From 2011–2012, 12% of cases were 3+ by IHC, 84% of them were amplified by FISH. Less than 1% of IHC score 0/1+ cases were amplified by FISH. Concordance between FISH and IHC increased from 83% to 97%.

Conclusions

Our quality control study demonstrates that HER2 positivity rate remained stable by FISH-technology but showed a significant variation by IHC over the analyzed 12 years. Improvement in concordance rate was due to standardization of pre-analytical factors, scoring and interpretation.

Marked heterogeneity of HER2/NEU gene amplification in endometrial serous carcinoma

Significant heterogeneity of HER2 protein expression has been recently observed in HER2 positive endometrial serous carcinomas. Tumor cells with HER2 overexpression and/or gene amplification in a heterogeneous tumor may represent a biologically more aggressive subclone that is clinically relevant to prognosis and potential targeted therapy. To correlate with HER2 protein heterogeneity, we investigated the heterogeneity of HER2/NEU gene amplification in endometrial serous carcinoma. A total of 17 endometrial serous carcinomas with heterogeneous HER2 protein expression were selected for the study, including nine cases with a 3+ and eight cases with a 2+ immunohistochemical score. Initial reflex HER2 FISH was available for seven of the eight 2+ cases, five of which showed HER2/NEU gene amplification. All 17 cases underwent repeat FISH targeting larger tumor tissue areas. Ten cases (72%) displayed striking heterogeneity of HER2/NEU gene copy number in the form of cluster amplification. Diffuse HER2 amplification was observed in four cases, no amplification was seen in three tumors. In cases with cluster amplification, HER2 protein overexpression by immunohistochemistry closely correlated at the cellular level with HER2/NEU gene amplification. In conclusion, the significant percentage of cases with heterogeneous HER2/NEU gene amplification indicates that the existing HER2 testing guidelines designed for breast cancer may not be applicable to endometrial serous carcinoma. Clinical testing on multiple different tumor samples or large tumor tissue sections is recommended for both immunohistochemistry and FISH assessment of HER2 status. Direct comparison with the HER2 immunostaining pattern may be helpful in detecting HER2 amplified areas in a heterogeneous tumor.

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.

Current Challenges for HER2 Testing in Diagnostic Pathology: State of the Art and Controversial Issues

HER2 overexpression and anti-HER2 agents represent probably the best story of success of individualized therapy in breast cancer. Due to the important therapeutic implications, the issue under the spotlight has been, since ever, the correct identification of true HER2 positivity on tissue specimens. Eligibility to anti-HER2 agents is strictly dependent on the demonstration of HER2 overexpression (by immunohistochemistry) or of HER2 gene amplification by in situ techniques (fluorescence in situ hybridization, FISH), however there are controversial issues involving cases with "equivocal" HER2 status based on conventional techniques (about 20% of specimens). In terms of HER2 expression a major debate is the presence of full-length and truncated forms of the protein and controversial clinical data have been reported on the therapeutic implications of these HER2 fragments. In terms of HER2 gene assessment, the occurrence of amplification of the chromosome 17 centromeric region (CEP17) has been proven responsible for misleading HER2 FISH results, precluding anti-HER2 based therapy to some patients. Finally HER2 activating mutations have been recently described as a biological mechanisms alternative to HER2 gene amplification. In this review we will focus on the controversies that pathologists and oncologists routinely face in the attempt to design the most tailored treatment for breast cancer patients. We will focus on the HER2 gene and on the protein, both at technical and interpretational levels.

Evaluation of the prognostic role of centromere 17 gain and HER2/topoisomerase II alpha gene status and protein expression in patients with breast cancer treated with anthracycline-containing adjuvant chemotherapy: pooled analysis of two Hellenic Cooperative Oncology Group (HeCOG) phase III trials

BACKGROUND

The HER2 gene has been established as a valid biological marker for the treatment of breast cancer patients with trastuzumab and probably other agents, such as paclitaxel and anthracyclines. The TOP2A gene has been associated with response to anthracyclines. Limited information exists on the relationship of HER2/TOP2A gene status in the presence of centromere 17 (CEP17) gain with outcome of patients treated with anthracycline-containing adjuvant chemotherapy.

METHODS

Formalin-fixed paraffin-embedded tumor tissue samples from 1031 patients with high-risk operable breast cancer, enrolled in two consecutive phase III trials, were assessed in a central laboratory by fluorescence in situ hybridization for HER2/TOP2A gene amplification and CEP17 gain (CEP17 probe). Amplification of HER2 and TOP2A were defined as a gene/CEP17 ratio of >2.2 and ≥2.0, respectively, or gene copy number higher than 6. Additionally, HER2, TopoIIa, ER/PgR and Ki67 protein expression was assessed by immunohistochemistry (IHC) and patients were classified according to their IHC phenotype. Treatment consisted of epirubicin-based adjuvant chemotherapy followed by hormonal therapy and radiation, as indicated.

RESULTS

HER2 amplification was found in 23.7% of the patients and TOP2A amplification in 10.1%. In total, 41.8% of HER2-amplified tumors demonstrated TOP2A co-amplification. The median (range) of HER2, TOP2A and CEP17 gain was 2.55 (0.70-45.15), 2.20 (0.70-26.15) and 2.00 (0.70-26.55), respectively. Forty percent of the tumors had CEP17 gain (51% of those with HER2 amplification). Adjusting for treatment groups in the Cox model, HER2 amplification, TOP2A amplification, CEP17 gain and HER2/TOP2A co-amplification were not associated with time to relapse or time to death.

CONCLUSION

HER2 amplification, TOP2A amplification, CEP17 gain and HER2/TOP2A co-amplification were not associated with outcome in high-risk breast cancer patients treated with anthracycline-based adjuvant chemotherapy.

TRIAL REGISTRATION

Australian New Zealand Clinical Trials Registry (ANZCTR) ACTRN12611000506998 and ACTRN12609001036202.

Lack of independent prognostic and predictive value of centromere 17 copy number changes in breast cancer patients with known HER2 and TOP2A status

The clinical benefit of anthracyclines has been connected to HER2 status, TOP2A status and centromere 17 copy numbers (CEN-17). Data from a clinical trial randomizing patients to anthracyclines was used to assess whether the number of CEN-17 in breast cancers may predict incremental responsiveness to anthracyclines besides what is obtained when used relatively to TOP2A and HER2. As cut sections of paraffin-embedded tissue are prone to truncation of nuclei, strict definition of ploidy levels is lacking. We therefore used normal breast tissue to assist define ploidy levels in cut sections. Fluorescence in situ hybridization (FISH) with centromere 17 (CEN-17) and TOP2A was performed on 120 normal breast specimens. The diploid CEN-17 copy number was reduced from the expected two signals in whole nuclei to an average of 1.68 signals per nucleus in cut sections of normal breast. Ploidy levels determined in normal breast were applied to data on 767 patients with known HER2 and TOP2A status randomized to anthracyclines in the DBCG 89D trial. CEN-17 ploidy levels were in cut sections from the 767 breast cancer patients established as: Haploid: ≤1.25 (10%), diploid: 1.26-2.09 (60%), triploid: 2.10-2.93 (21%), tetraploid: 2.94-3.77 (5%) or higher ploidy: ≥3.78 (4%). Amplification of HER2 and deletion of TOP2A were frequently observed in tumors with a high ploidy level. In univariate analyses increasing ploidy was associated with decreased disease-free survival (DFS) (P=0.0001) and overall survival (OS) (P<0.0001). However, in multivariate analysis CEN-17 was not established as an independent prognostic factor and was neither a statistically significant predictor of benefit from CEF (Cyclophosphamide/Epirubicin/5-Fluorouracil) compared to CMF (Cyclophosphamide/Methotrexate/5-Fluorouracil) (P(Interaction) 0.39 for DFS and 0.67 for OS). In conclusion, CEN-17 levels do not independently from TOP2A/CEN-17 ratio identify breast cancer patients who achieve an incremental benefit from adjuvant anthracyclines.