Validation and workflow optimization of human epidermal growth factor receptor 2 testing using INFORM HER2 dual-color in situ hybridization

Validation of Dual-Color Dual In Situ Hybridization for HER2/neu Gene in Breast Cancer

CONTEXT.—

Human epidermal growth factor (HER2/neu) gene amplification, a poor prognostic factor in invasive breast cancer, has shown substantial utility as a predictive marker, with significantly improved survival following anti-HER2 therapies like trastuzumab. Dual-color dual in situ hybridization (D-DISH), a recently introduced fully automated assay for HER2/neu evaluation on light microscopy, has several advantages over fluorescence in situ hybridization (FISH).

OBJECTIVE.—

To standardize and validate the D-DISH assay using FISH as the gold standard and assess interobserver reproducibility in interpreting the D-DISH assay.

DESIGN.—

D-DISH was performed using the latest HER2 Dual ISH DNA Probe Cocktail assay (Ventana Medical Systems Inc, Tucson, Arizona) in 148 cases of invasive breast cancer. The same block was used for performing immunohistochemistry by Ventana PATHWAY anti-HER2/neu (4B5) antibody and FISH assay by ZytoLight SPEC ERBB2/CEN17 Dual Color Probe. D-DISH was separately interpreted by 4 pathologists blinded to FISH results.

RESULTS.—

Concordance of 98.65% and a Cohen κ value of 0.97 were observed between FISH and D-DISH. Intraclass correlation coefficient (0.93-0.97) and κ values (0.98-1.0) for interobserver reproducibility showed almost perfect agreement by D-DISH. Interobserver reproducibility was also evaluated for genomic heterogeneity, HER2 group categorization, and polysomy (κ values 0.42-0.74, 0.89-0.93, and 0.98-1.0, respectively).

CONCLUSIONS.—

We successfully validated the latest version of D-DISH assay as a substitute for FISH in predicting HER2 gene status with significant interobserver reproducibility, concluding that this D-DISH assay may be introduced in routine diagnostic services as a reflex test to ascertain HER2 gene status.

HER2 copy number determination in breast cancer using the highly sensitive droplet digital PCR method

Human epidermal growth factor receptor 2 (HER)-positive breast cancer (BC) is characterized by an aggressive clinical course. In the case of HER2 overexpression/amplification, patients benefit from HER2-targeting therapies. Standardized diagnostic HER2 assessment includes immunohistochemistry (IHC) and/or in situ hybridization (ISH). The aim of this study was to compare this "gold standard" with the Droplet Digital™ polymerase chain reaction (ddPCR), a method that allows sensitive and precise detection of copy number variations (CNV) in FFPE (formalin-fixed, paraffin-embedded) DNA samples. Partitioning of the PCR reaction into 20,000 droplets enables a precise quantitative "CN" discrimination also in heterogeneous samples. FFPE breast cancer samples (n = 170) with routinely assessed HER2 status by IHC/ISH were retrospectively analyzed using the ddPCR CNV ERBB2 assay. Comparison of HER2 status assessment by the two methods revealed concordant results in 92.9% (158/170) of the cases. Discrepant cases were verified and interpreted. For ddPCR, a cut off value of 3 HER2 copies was set to distinguish between HER2-negative and HER2-positive BC. Results obtained with the ddPCR CNV ERBB2 assay were consistent and reproducible, and serial dilutions demonstrated a high stability and sensitivity of the method. The ddPCR CNV ERBB2 assay may be a specific and convenient tool to quantify HER2 copy numbers in BC samples. In our study, this method showed high reproducibility in accuracy of HER2 assessment compared to IHC/ISH analysis.

A sandwich-type electrochemical immunosensor for sensitive detection of HER2 based on dual signal amplification of La-MOF-PbO2 and PEI-MoS2NFs composites

In recent decades, the incidence of breast cancer has increased year by year, posing a serious threat to human health and quality of life, and about 30% of breast cancer patients have human epidermal growth factor receptor 2 (HER2) overexpression. Therefore, HER2 has become an important biomarker and indicator for the clinical evaluation of breast cancer in diagnosis, prognosis and recurrence. In this work, polyethyleneimine functionalized MoS₂ nanoflowers (PEI-MoS₂NFs) with good electrical conductivity and abundant active binding sites were designed and employed as a sensing platform for immobilizing the primary antibody of HER2 (Ab₁). In addition, a La-MOF-PbO₂ composite with a large specific surface area and good conductivity was used to load lots of electroactive toluidine blue (TB) and the secondary antibody of HER2 (Ab₂) via gold nanoparticles (AuNPs) as the linker. Thus, the constructed sandwich-type electrochemical immunosensor was applied for sensitive detection of HER2, which showed a wide linear range from 100 fg mL^-1 to 10 μg mL^-1 with a lower limit of detection of 15.64 fg mL^-1. Therefore, the resulting immunosensor in this study would have a potential application in clinical bioanalysis.

Detection of ERBB2 and CEN17 signals in fluorescent in situ hybridization and dual in situ hybridization for guiding breast cancer HER2 target therapy

The overexpression of the human epidermal growth factor receptor 2 (HER2) is a predictive biomarker in therapeutic effects for metastatic breast cancer. Accurate HER2 testing is critical for determining the most suitable treatment for patients. Fluorescent in situ hybridization (FISH) and dual in situ hybridization (DISH) have been recognized as FDA-approved methods to determine HER2 overexpression. However, analysis of HER2 overexpression is challenging. Firstly, the boundaries of cells are often unclear and blurry, with large variations in cell shapes and signals, making it challenging to identify the precise areas of HER2-related cells. Secondly, the use of sparsely labeled data, where some unlabeled HER2-related cells are classified as background, can significantly confuse fully supervised AI learning and result in unsatisfactory model outcomes. In this study, we present a weakly supervised Cascade R-CNN (W-CRCNN) model to automatically detect HER2 overexpression in HER2 DISH and FISH images acquired from clinical breast cancer samples. The experimental results demonstrate that the proposed W-CRCNN achieves excellent results in identification of HER2 amplification in three datasets, including two DISH datasets and a FISH dataset. For the FISH dataset, the proposed W-CRCNN achieves an accuracy of 0.970±0.022, precision of 0.974±0.028, recall of 0.917±0.065, F1-score of 0.943±0.042 and Jaccard Index of 0.899±0.073. For DISH datasets, the proposed W-CRCNN achieves an accuracy of 0.971±0.024, precision of 0.969±0.015, recall of 0.925±0.020, F1-score of 0.947±0.036 and Jaccard Index of 0.884±0.103 for dataset 1, and an accuracy of 0.978±0.011, precision of 0.975±0.011, recall of 0.918±0.038, F1-score of 0.946±0.030 and Jaccard Index of 0.884±0.052 for dataset 2, respectively. In comparison with the benchmark methods, the proposed W-CRCNN significantly outperforms all the benchmark approaches in identification of HER2 overexpression in FISH and DISH datasets (p<0.05). With the high degree of accuracy, precision and recall , the results show that the proposed method in DISH analysis for assessment of HER2 overexpression in breast cancer patients has significant potential to assist precision medicine.

HER2 Dual In Situ Hybridization: Correlations and Cautions

CONTEXT.—

Accurate HER2 testing in breast cancer is crucial for appropriate precision therapy. HER2 testing is most commonly accomplished by a combination of immunohistochemistry and in situ hybridization techniques, as gene amplification is closely tied to protein overexpression. During the last 5+ years, brightfield dual in situ hybridization (DISH) has replaced fluorescence methods (fluorescence in situ hybridization [FISH]) in some laboratories.

OBJECTIVE.—

To analyze routine HER2 DISH performance in the field.

DESIGN.—

We reviewed our experience with HER2 DISH performed at outside laboratories and referred for patient care.

RESULTS.—

Of 273 identified retrospective DISH results, 55 had repeated FISH testing at our institution; 7 (13%) were discordant. Additional cases had technical flaws hampering appropriate scoring. In 23 cases (42%), HER2 DISH was performed without immunohistochemistry. Slide review of a prospective cohort of 42 consecutive DISH cases revealed 14 (33%) with technical or interpretative limitations potentially jeopardizing results. Commonly identified problems include lack of or weak signals in most tumor cells, and silver precipitate or red signals outside of nuclei, resulting in false-negative or false-positive interpretations, respectively. Further, 44% (24 of 55) of DISH reports lacked complete data, specifically average HER2 signals/cell.

CONCLUSIONS.—

While HER2 DISH can be an efficient and effective alternative to FISH, we illustrate pitfalls and reinforce that careful attention to slide quality and technical parameters are critically important. HER2 DISH cotesting with immunohistochemistry could help minimize false-negative or false-positive HER2 results.

Evaluation of analytical accuracy of HER2 status in patients with breast cancer: Comparison of HER2 GPA with HER2 IHC and HER2 FISH

Human epidermal growth factor receptor 2 (HER2) gene status and overexpression, occurring in ~ 13.6% of primary breast cancers, is essential for identifying patients likely to benefit from biological treatment. In this method of evaluation study, we tested and compared the HER2 gene-protein assay (GPA) with routine HER2 immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH). The GPA was evaluated using 67 formalin-fixed paraffin-embedded (FFPE) HER2 equivoval IHC (2+) breast cancer tissue samples. Overall, agreement between GPA silver in situ hybridization (SISH) and FISH was 91.9% (57/62). Regression analysis revealed slightly higher, but non-significant difference in HER2/chromosome enumeration probe 17 (CEP17) ratio for GPA as compared to FISH (p = 0.074). Intraclass correlation coefficients (ICCs) of 0.94 and Spearman´s rank correlation coefficients of 0.93 (p < 0.0001) for FISH and GPA SISH suggested strong inter-observer association for methods with one observer counting on average 0.23 significant higher for GPA SISH (p = 0.014). Intra-observer IHC method reproducibility was 52.6% (κ = 0.3122, p = 0.004) and 79.7% (κ = 0.6428, p = 0.9197), suggesting fair significant and substantial non-significant difference between tests for reviewers. Inter-observer reproducibility for IHC methods was 53%. While inter-observer reproducibility for experienced IHC interpretation suggested significant differences (κ = 0.3636, p = 0.0332), unexperienced interpretation of IHC GPA suggested fair non-significant difference between reviewers (κ = 0.3101, p = 0.0747). Using FISH as reference, the diagnostic indices for GPA SISH were as follows: sensitivity 100%, specificity 95% and accuracy 92%. Inaccuracy between tests was in 80% of cases due to ISH categorization as equivocal by one of the methods. IHC results highlight that it may be beneficial with a method for simultaneously visualization of HER2 gene and protein status.

Impedimetric aptasensing of the breast cancer biomarker HER2 using a glassy carbon electrode modified with gold nanoparticles in a composite consisting of electrochemically reduced graphene oxide and single-walled carbon nanotubes

A method is presented for electrochemical determination of the breast cancer biomarker HER2. A glassy carbon electrode (GCE) was modified with densely packed gold nanoparticles placed on a composite consisting of electrochemically reduced graphene oxide and single walled carbon nanotubes (ErGO-SWCNTs). An aptamer directed against HER2 was then immobilized ono the GCE. The modified GCE was characterized by cyclic voltammetry, differential pulse voltammetry and electrochemical impedance spectroscopy. The immobilized aptamer selectively recognizes HER2 on the electrode interface, and this leads to an increased charge transfer resistance (R_ct) of the electrode when using ferri/ferro-cyanide as the electrochemical probe. The method has a low limit of detection (50 fg·mL^-1) and a wide analytical range (0.1 pg·mL^-1 to 1 ng·mL^-1). The assay is highly reproducible and specific. Clinical application was demonstrated by analysis of the HER2 levels in serum samples, and sera of breast cancer patients were successfully discriminated from sera of healthy persons. Graphical abstract An electrochemical aptasensor for HER2 is described that is based on the immobilization of anti-HER2 aptamer on a glassy carbon electrode modified with a nanocomposite prepred fromreduced graphene oxide, carbon nanotubes and gold nanoparticles.

What to expect from the 2018 ASCO/CAP HER2 guideline in the reflex in situ hybridization test of immunohistochemically equivocal 2+ cases?

To evaluate the effect of the 2018 ASCO/CAP guideline in the identification of HER2-positive breast carcinomas (BC) in reflex in situ hybridization (ISH) test. A total of 592 primary invasive BC cases from before and after the publication of the updated ASCO/CAP guideline were evaluated for HER2 amplification by silver ISH according to the 2013 and 2018 guidelines. Cases were mostly (95%) HER2 equivocal by immunohistochemistry (IHC), not centrally reviewed. Other reasons for referring cases were IHC confirmation, IHC discordancy (either between needle-core-biopsy (NCB) and surgical excision specimen (SES) or between different laboratories) and IHC result unexpected for histopathologic features. Cases evaluated with the 2013 guideline (1st cohort) were 14.6% HER2-positive, decreasing significantly after the reclassification with the 2018 guideline due to the exclusion of group 2 cases without HER2 protein overexpression. Cases studied after the implementation of the 2018 guideline (2nd cohort) were 8.7% HER2-positive, a frequency that was not significantly different from the reclassification of the 1st cohort with the 2018 guideline. All cases referred for IHC confirmation had the expected ISH result. Cases with IHC discordancy between NCB and SES were ISH concordant. Only one out of 14 cases with an IHC score 3+ and classified as histological grade 1 or with a Ki67 below 10% was classified as ISH HER2-positive. The 2018 ASCO/CAP guideline resulted in a decrease of HER2-positive cases in reflex ISH test, selecting less patients for anti-HER2-targeted therapy.

Ancillary studies in cytology: Secondary or necessary?

Ancillary studies are rapidly becoming an integral and necessary aspect of cytologic analysis. In addition to morphologic features, cytologic specimens contain an enormous amount of information content within their molecules that should be tapped to add value to these samples. Fortunately, a large number of existing and emerging technologies exist to provide access to this information. Adoption of these technologies will require continued attention to fundamental aspects of specimen procurement, handling, and processing to ensure testing accuracy. Successful implementation of ancillary studies will depend on rigorous validation of assays and the development of evidence-based guidelines for their use in patients. Cytopathologists must embrace the role of ancillary test stewardship to ensure the future clinical use of cytologic specimens.

Comparison of HER2 status determination methods in HER2 (2+) patients: Manual fluorescent in situ hybridization (FISH) vs. dual silver enhanced in situ hybridization (SISH)

HER2 amplification has been demonstrated in 15-25% of invasive breast carcinomas and can be assessed using immunohistochemical and in situ hybridization methods. Here, we compared the accuracy of dual SISH to manual FISH in HER2 (2+) breast carcinoma and evaluated the feasibility of dual SISH method in routine practice. Sixty HER2 (2+) consecutive tumor samples diagnosed between January 2009 and February 2013 were selected. Demographic, histological and immunohistochemical features and FISH results were recruited from patient records and compared to dual SISH results. Nine (15%) of the 60 tumor samples were excluded from statistical analysis due to lack of interpretable SISH signals. HER2 staining percentages by immunohistochemistry differed between 20 and 80%. HER2 amplification was shown in 7 (13.7%) and 8 (15.7%) patients by FISH and SISH, respectively. Very good agreement was observed between FISH and SISH methods (kappa value: 0.92). Significant correlation was found between HER2 staining percentage and FISH positivity, in contrast to SISH positivity (p=0.012 vs. p=0.069). Our results are consistent with previously reported literature, indicating SISH can be used to determine HER2 status. However, preanalytical and analytical problems may cause inadequate or uncountable signals, making interpretation impossible for the pathologist and highlighting the importance of standardization and quality control programs.

Addressing the challenges of applying precision oncology

Precision oncology is described as the matching of the most accurate and effective treatments with the individual cancer patient. Identification of important gene mutations, such as BRCA1/2 that drive carcinogenesis, helped pave the way for precision diagnosis in cancer. Oncoproteins and their signaling pathways have been extensively studied, leading to the development of target-based precision therapies against several types of cancers. Although many challenges exist that could hinder the success of precision oncology, cutting-edge tools for precision diagnosis and precision therapy will assist in overcoming many of these difficulties. Based on the continued rapid progression of genomic analysis, drug development, and clinical trial design, precision oncology will ultimately become the standard of care in cancer therapeutics.

Automated Bright-Field Dual-Color In Situ Hybridization for MDM2: Interobserver Reproducibility and Correlation With Fluorescence In Situ Hybridization in a Series of Soft Tissue Consults

CONTEXT

-Atypical lipomatous tumors/well-differentiated liposarcomas contain alterations in the 12q13-15 region resulting in amplification of MDM2 and nearby genes. Identifying MDM2 amplification is a useful ancillary test, as the histologic mimics of atypical lipomatous tumors/well-differentiated liposarcomas have consistently shown a lack of MDM2 amplification.

OBJECTIVE

-To assess the interobserver reproducibility of a bright-field assay for MDM2 amplification (dual-color, dual-hapten in situ hybridization [DDISH]) among reviewers with varying degrees of experience with the assay and to assess the concordance of MDM2 DDISH with MDM2 fluorescence in situ hybridization (FISH).

DESIGN

-In total, 102 cases were assessed in parallel for MDM2 by FISH and DDISH. MDM2 amplification was defined as an MDM2 to chromosome 12 ratio of 2.0 or greater, whereas an MDM2 to chromosome 12 ratio of less than 2 was nonamplified. Fluorescence in situ hybridization was scored in the routine clinical laboratory and DDISH was evaluated by 3 different pathologists blinded to the final diagnosis and FISH results.

RESULTS

-Fluorescence in situ hybridization categorized 27 cases (26%) as MDM2 amplified and 75 cases (74%) as nonamplified; the consensus DDISH diagnosis was 98% concordant with FISH. Agreement between MDM2 DDISH by each reviewer and MDM2 FISH was highly concordant (99%, 98%, and 98%, respectively, for reviewers 1, 2 and 3). The κ agreement of the 3 reviewers scoring DDISH was excellent (κ = 0.949, 0.95, and 0.95, respectively, for reviewers 1, 2, and 3).

CONCLUSIONS

-This study highlights excellent concordance between DDISH and FISH in MDM2 copy number assessment. Moreover, excellent interobserver reproducibility of the DDISH assay was found among reviewers with varying levels of experience evaluating bright-field assays.

Comparison of HER2 Dual-Color and Fluorescence In Situ Hybridization in Breast Cancer: A Cohort Study Emphasizing Equivocal Cases

OBJECTIVES

Human epidermal growth factor receptor 2 (HER2; ERBB2 gene) is of prognostic and predictive significance in breast carcinoma. Both fluorescence in situ hybridization (FISH) and dual-color in situ hybridization (DISH) methods are available. DISH and FISH are highly concordant in validation studies, but differences may be more prevalent in the equivocal range. Our goal was to compare FISH and DISH on a cohort enriched for equivocal cases, with respect to HER2 determination.

METHODS

The cohort was enriched for equivocal (2+) cases. DISH and FISH were evaluated using standard protocols and the results compared with respect to HER2 status, HER2 copy number, and HER2/chromosome 17 (Chr17) ratio.

RESULTS

In total, 109 cases were identified. The agreement rate of DISH with FISH was 74%. The mean ± SD HER2/Chr17 ratio by DISH was 1.63 ± 0.08 vs 1.59 ± 0.26 by FISH (P = .45). The mean ± SD HER2 copy number by DISH was 4.56 ± 0.45 vs 4.75 ± 1.08 by FISH (P = .004). Individual signals were more easily resolved using FISH in cases with higher copy numbers.

CONCLUSIONS

In our cohort enriched for equivocal cases, the numerical values of HER2 copy number were significantly lower using DISH, resulting in discordances. Although DISH is a valid method, variations with FISH may be expected in high-equivocal cases and in quality assurance activities.

Optimal Scoring of Brightfield Dual-Color In Situ Hybridization for Evaluation of HER2 Amplification in Breast Carcinoma: How Many Cells Are Enough?

OBJECTIVES

The purpose of this study was to determine the optimum number of cells that should be counted when scoring human epidermal growth factor receptor 2 (HER2) brightfield dual-color in situ hybridization (BDISH), including cases with HER2/chromosome 17 (Chr17) ratios in the 1.80 to 2.20 range.

METHODS IN TOTAL,

131 cases of breast carcinoma with HER2 immunohistochemistry and BDISH were included. For cases with a HER2/Chr17 ratio of less than 1.80 or more than 2.20 (n = 115), BDISH scoring was performed for 60 cells using three tumor fields, and for cases with a HER2/Chr17 ratio of 1.80 to 2.20 (n = 16), scoring was performed for 120 cells using six tumor fields. Mean HER2/Chr17 ratio and HER2 copy number were calculated for cumulative cell counts.

RESULTS

The HER2 status as determined by the HER2/Chr17 ratio or HER2 copy number was unchanged following counting of additional cells in 100% of cases with ratio of less than 1.80 or more than 2.20. The HER2 status of two cases with ratios of 1.80 to 2.20 changed from positive to negative following counting of 120 cells.

CONCLUSIONS

Our findings support recommendations to score 20 nuclei in conjunction with careful assessment of immunohistochemistry and scan of the BDISH slide to identify areas of heterogeneity. Scoring of additional cells/fields is likely not of benefit and might be a disadvantage since the scorer moves out of the area of strongest signal.

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.

Clinical Significance of Substaging and HER2 Expression in Papillary Nonmuscle Invasive Urothelial Cancers of the Urinary Bladder

The study aimed to verify the prognostic utility, therapeutic application and clinical benefits of tumor substaging and HER2 status in papillary non-muscle invasive bladder cancer (NMIBC). Select NMIBC transurethral resection specimens from 141 patients were used to construct tissue microarrays for assessing the substaging, HER2 protein expression by immunohistochemistry (HER2-IHC) and gene amplification by dual-color silver in situ hybridization (HER2-SISH). Substages were identified by the differing depth of tumor invasion (pTa / pT1a / pT1b / pT1c). HER2 protein expression was semiquantitatively analyzed and grouped into negative (score 0, 1+) and positive (score 2+, 3+). Other clinicopathological variables were also investigated. For NMIBC, HER2-IHC and HER2-SISH showed positive results in 6/141 (4.3%) and 4/141 (2.8%) respectively, which correlated well with tumor substaging. In multivariate analysis, substaging, HER2-IHC, and HER2-SISH were found to be independent predictors of progression-free survival (P < 0.001, P < 0.001, P = 0.031). HER2-IHC was the sole independent predictor of recurrent free survival in NMIBC (P = 0.017). It is suggested that tumor substaging and HER2 status are independent predictive markers for tumor progression or recurrence, and thus could be included in diagnostic and therapeutic management for NMIBC.

Comparison of the 2007 and 2013 ASCO/CAP evaluation systems for HER2 amplification in breast cancer

It has been proven that chromosome 17 centromere (CEP17) amplification causes misleading human epidermal growth factor receptor 2 (HER2) gene fluorescence in situ hybridization (FISH) results, precluding anti-HER2-based therapy in some patients with breast carcinoma. We used the 2013 American Society of Clinical Oncology/College of American Pathologists (ASCO/CAP) scoring criteria to evaluate HER2 amplification status in 175 cases of breast carcinoma with chromosome 17 polysomy. We used immunohistochemistry (IHC) to determine the HER2 amplification status, and 2-color FISH to detect CEP17, and reviewed the results of initial evaluation using the 2007 ASCO/CAP criteria. Of the 175 cases, 17, 95, and 63 were IHC 0/1+, 2+, and 3+, respectively. Evaluation of IHC HER2 status according to the 2013 ASCO/CAP criteria identified significantly more HER2-positive cases compared to cases evaluated using the 2007 criteria (p<0.05). When the FISH results were evaluated in parallel with the 2013 criteria, we found that 22 cases were not HER2-negative despite the presence of polysomy 17, which, according to the 2013 criteria, indicates HER2-positive status. Our findings indicate that in breast carcinoma, HER2 status in the presence of polysomy 17 may vary with the scoring criteria used. In turn, performing FISH and evaluating samples using the 2013 ASCO/CAP criteria means that more patients with breast cancer may be appropriate for targeted treatment with trastuzumab, potentially improving their outcome.