Analysis of aneusomy level and HER-2 gene copy number and their effect on amplification rate in breast cancer specimens read as 2+ in immunohistochemical analysis

A clinicopathological study and survival analysis of 99 breast cancers with HER2/CEP17 ratio ≥ 2.0 and an average HER2 copy number < 4.0 per cell in China

BACKGROUND

Breast cancer patients of American Society of Clinical Oncology and the College of American Pathologists (ASCO/CAP) Group 2 were all HER2-negative according to the 2018 guideline, not HER2-positive as defined in the 2013 guideline.

METHODS

We aims to elucidate the unique clinicopathological features of ASCO/CAP Group 2 patients by comparing with classic HER2-nonamplified cancers, and reveal the efficacy of the former to anti-HER2 therapy. The clinicopathological features, treatment and prognosis information of 99 patients between 2014 and 2018 were collected. HER2 status was re-defined using the updated recommendations.

RESULTS

Of the 99 ASCO/CAP Group 2 tumors, 25.5% (25/99) tumors were immunohistochemical (IHC) 0/1+ and 74.7% (74/99) tumors were IHC 2+. According to the updated 2018 guideline, all of them were HER2 negative. When compared to ASCO/CAP Group 5, patients of ASCO/CAP Group 2 displayed higher ratio of histological grade 3 (P = .03), high Ki67 proliferation index (P = .03) and pN3 (more than 9 lymph nodes metastasis, P = .02), and lower estrogen receptor (ER) positivity (P = .04). There was no statistical difference in the survival of patients received anti-HER2 therapy and patients not received anti-HER2 therapy.

CONCLUSIONS

Patients of ASCO/CAP Group 2 did not received apparent benefit from anti-HER2 treatment. Although according to the updated guidelines and latest reports, HER2 is negative, but when compared with classic HER2-nonamplified cancers, patients of this group seemed to be more aggressive. We suggest that this group still be regarded as an independent category, in order to accumulate more cases in the future to expand the scope of research.

Addition of Chromosome 17 Polysomy and HER2 Amplification Status Improves the Accuracy of Clinicopathological Factor-Based Progression Risk Stratification and Tumor Grading of Non-Muscle-Invasive Bladder Cancer

Progression of non-muscle-invasive bladder cancer (NMIBC) to muscle-invasive disease (MIBC) significantly worsens life expectancy. Its risk can be assessed by clinicopathological factors according to international guidelines. However, additional molecular markers are needed to refine and improve the prediction. Therefore, in the present study, we aimed to predict the progression of NMIBCs to MIBC by assessing p53 expression, polysomy of chromosome 17 (Chr17) and HER2 status in the tissue specimens of the tumors of 90 NMIBC patients. Median follow-up was 77 months (range 2−158). Patients with Chr17 polysomy or HER2 gene amplification had a higher rate of disease progression (hazard ratio: 7.44; p < 0.001 and 4.04; p = 0.033, respectively; univariate Cox regression). Multivariable Cox regression models demonstrated that the addition of either Chr17 polysomy or HER2 gene amplification status to the European Association of Urology (EAU) progression risk score increases the c-index (from 0.741/EAU/ to 0.793 and 0.755, respectively), indicating that Chr17 polysomy/HER2 amplification status information improves the accuracy of the EAU risk table in predicting disease progression. HER2/Chr17 in situ hybridization can be used to select non-progressive cases not requiring strict follow-up, by reclassifying non-HER2-amplified, non-polysomic NMIBCs from the high- and very high-risk groups of EAU to the intermediate-risk group.

The frequency and clinical significance of centromere enumeration probe 17 alterations in HER2 immunohistochemistry-equivocal invasive breast cancer

Background and aims

Chromosome 17 alterations affect the assessment of HER2 gene amplification in breast cancer (BC), but its clinical significance remains unclear. This study aimed to identify the prevalence of centromere enumeration probe 17 (CEP17) alterations, and its correlation with response to neoadjuvant therapy (NAT) in BC patients with human epidermal growth factor receptor 2 (HER2) immunohistochemistry‐equivocal score.

Methods and results

A large BC cohort (n = 6049) with HER2 immunohistochemistry score 2+ and florescent in‐situ hybridisation (FISH) results was included to assess the prevalence of CEP17 alterations. Another cohort (n = 885) with available clinicopathological data was used to evaluate the effect of CEP17 in the setting of NAT. HER2‐amplified tumours with monosomy 17 (CEP17 copy number < 1.5 per nucleus), normal 17 (CEP17 1.5–< 3.0) and polysomy 17 (CEP17 ≥ 3.0) were observed in 16, 59 and 25%, respectively, compared with 3, 74 and 23%, respectively, in HER2‐non‐amplified tumours. There was no significant relationship between CEP17 alterations and pathological complete response (pCR) rate in both HER2‐amplified and HER2‐non‐amplified tumours. The independent predictors of pCR were oestrogen (ER) negativity in HER2‐amplified tumours [ER negative versus positive; odds ratio (OR) = 11.80; 95% confidence interval (CI) = 1.37–102.00; P = 0.02], and histological grade 3 in HER2 non‐amplified tumours (3 versus 1, 2; OR = 5.54; 95% CI = 1.61–19.00; P = 0.007).

Conclusion

The impacts of CEP17 alterations are not as strong as those of HER2/CEP17 ratio and HER2 copy number. The hormonal receptors status and tumour histological grade are more useful to identify BC patients with a HER2 immunohistochemistry‐equivocal score who would benefit from NAT.

HER2 status in breast cancer: changes in guidelines and complicating factors for interpretation

Human epidermal growth factor receptor 2 (HER2) protein overexpression and/or HER2 gene amplification is found in about 20% of invasive breast cancers. It is a sole predictive marker for treatment benefits from HER2 targeted therapy and thus, HER2 testing is a routine practice for newly diagnosed breast cancer in pathology. Currently, HER2 immunohistochemistry (IHC) is used for a screening test, and in situ hybridization is used as a confirmation test for HER2 IHC equivocal cases. Since the American Society of Clinical Oncology (ASCO)/College of American Pathologists (CAP) guidelines on HER2 testing was first released in 2007, it has been updated to provide clear instructions for HER2 testing and accurate determination of HER2 status in breast cancer. During HER2 interpretation, some pitfalls such as intratumoral HER2 heterogeneity and increase in chromosome enumeration probe 17 signals may lead to inaccurate assessment of HER2 status. Moreover, HER2 status can be altered after neoadjuvant chemotherapy or during metastatic progression, due to biologic or methodologic issues. This review addresses recent updates of ASCO/CAP guidelines and factors complicating in the interpretation of HER2 status in breast cancers.

Utility of cytopathological specimens and an automated image analysis for the evaluation of HER2 status and intratumor heterogeneity in breast carcinoma

OBJECTIVES

Although updated HER2 testing guidelines have been improved by a collaboration between the American Society of Clinical Oncology (ASCO) and the College of American Pathologists (CAP) in 2013, HER2 evaluation is still problematic because of issues involving CEP17 polysomy, heterogeneity, and HER2 score 2+ cases. The aim of this retrospective study was to evaluate the relationship between HER2 gene heterogeneity, or so called CEP17 polysomy, using breast carcinoma cells sampled by scraping and the IHC score graded by automated image analysis using whole slide image.

MATERIAL AND METHODS

We randomly selected 23 breast carcinoma cases with a HER2 score 0, 24 cases with a HER2 score 1+, 24 cases with HER2 score 2+, and 23 cases with HER2 score 3+ from the records of patients with breast cancer at Hiroshima University Hospital. We compared the results of fluorescent in situ hybridization (FISH) using formalin-fixed, paraffin-embedded (FFPE) tissues and cytological samples and compared the HER2 score calculated using an automated image analysis using wholly scanned slide images and visual counting.

RESULTS

We successfully performed the FISH assay in 78 of 94 cases (83%) using FFPE tissues and in all 94 (100%) cases using cytological samples. Frequency of both HER2 amplification and CEP17 polysomy was higher when cytological samples were used than when FFPE tissue was used. Frequency of HER2 heterogeneity using cytological samples was higher that than using FFPE tissue, except for the IHC score 3+ cases.

CONCLUSIONS

When assessment of HER2 status based on FISH using FFPE tissue cannot be accomplished, FISH using cytological samples should be considered. When intensity of HER2 is heterogeneous in the tumor tissue, particularly in cases regarded as score 2+, they should be evaluated by automated image analysis using the whole slide image.

HER2 intratumoral heterogeneity analyses by concurrent HER2 gene and protein assessment for the prognosis of HER2 negative invasive breast cancer patients

HER2 gene-protein assay (GPA) is a new method for the simultaneous evaluation of HER2 immunohistochemistry (IHC) and HER2 dual in situ hybridization (DISH) on single tissue sections of breast cancer. We investigated the presence of HER2 gene and protein discrepancy and HER2-heterogeneity using HER2-GPA. HER2 status was analyzed for the correlation between the presence of HER2-heterogeneity and patient prognosis. Consecutive 280 invasive breast cancer were examined. Statuses of HER2 protein and gene were evaluated in whole tumor sections of HER2 GPA slides. HER2 protein and gene combination patterns were classified to six phenotypic and genotypic types for each case, as well as at individual cell levels: (A) IHC and DISH positive; (B) IHC positive and DISH negative; (C) IHC equivocal and DISH positive; (D) IHC equivocal and DISH negative; (E) IHC negative and DISH positive; and (F) IHC and DISH negative. The presence of HER2-heterogeneity was determined by the existence of at least two of six types within one tumor. HER2-IHC positive patients had significantly worse survival than IHC negative patients and HER2-DISH positive patients had significantly worse survival than DISH negative patients. HER2 IHC negative and DISH positive patients had significantly worse recurrence-free survival than IHC and DISH negative patients. In the HER2 IHC and DISH negative group, the HER2 heterogeneous group had significantly worse survival than the nonheterogeneous group. Notably, among triple negative breast cancer (TNBC), the HER2 heterogeneous group had significantly worse survival than the nonheterogeneous group. Our study suggests that the presence of HER2-heterogeneity might be a prognostic factor in HER2 negative breast cancer patients, especially in TNBC.

HER2 in situ hybridization in breast cancer: clinical implications of polysomy 17 and genetic heterogeneity

Trastuzumab-containing therapy is a standard of care for patients with HER2+ breast cancer. HER2 status is routinely assigned using in situ hybridization to assess HER2 gene amplification, but interpretation of in situ hybridization results may be challenging in tumors with chromosome 17 polysomy or intratumoral genetic heterogeneity. Apparent chromosome 17 polysomy, defined by increased chromosome enumeration probe 17 (CEP17) signal number, is a common genetic aberration in breast cancer and represents an alternative mechanism for increasing HER2 copy number. Some studies have linked elevated CEP17 count ('polysomy') with adverse clinicopathologic features and HER2 overexpression, although there are numerous discrepancies in the literature. There is evidence that elevated CEP17 ('polysomy') count might account for trastuzumab response in tumors with normal HER2:CEP17 ratios. Nonetheless, recent studies establish that apparent 'polysomy' (CEP17 increase) is usually related to focal pericentromeric gains rather than true polysomy. Assigning HER2 status may also be complex where multiple cell subclones with distinct HER2 amplification characteristics coexist within the same tumor. Such genetic heterogeneity affects up to 40% of breast cancers when assessed according to a College of American Pathologists guideline, although other definitions have been proposed. Recent data have associated heterogeneity with unfavorable clinicopathologic variables and poor prognosis. Genetically heterogeneous tumors harboring HER2-amplified subclones have the potential to benefit from trastuzumab, but this has yet to be evaluated in clinical studies. In this review, we discuss the implications of apparent polysomy 17 and genetic heterogeneity for assigning HER2 status in clinical practice. Among our recommendations, we support the use of mean HER2 copy number rather than HER2:CEP17 ratio to define HER2 positivity in cases where coamplification of the centromere might mask HER2 amplification. We also highlight a need to harmonize in situ hybridization scoring methodology to support accurate HER2 status determination, particularly where there is evidence of heterogeneity.

Chromosome 17 polysomy: correlation with histological parameters and HER2NEU gene amplification

Aims

HER2NEU gene amplification is present in the majority of invasive breast carcinomas that have HER2 protein overexpression. A subset of breast cancers harbour an increased chromosome 17 (CEP17) copy number (polysomy 17). We investigated the clinicopathologic significance of polysomy 17 in correlation with various histological parameters and HER2NEU gene amplification.

Methods

We collected the surgical specimens of 266 consecutive cases of primary invasive breast carcinomas. HER2NEU gene status and CEP17 copy numbers were assessed by fluorescent in situ hybridisation (FISH). Chromosome 17 polysomy was determined by the presence of ≥3 average CEP17 signals per nucleus.

Results

63 tumours (23.7%) harboured polysomy 17. Carcinomas with polysomy 17 were associated with adverse histological indicators including high histological grade, high nuclear grade, poor Nottingham Prognostic Index, advanced local tumour extent and progesterone receptor negativity. Polysomy 17 was common to HER2NEU amplified and unamplified tumours, and more frequently observed in HER2NEU unamplified (71.4%) cases.

Conclusions

In the absence of the gene amplification, HER2 protein overexpression may be explained by other mechanisms including polysomy 17.

HER2 expression in breast cancer with nonamplified HER2 and gains of chromosome 17 centromere

Gains of chromosome 17 centromere (CEP17) may be accompanied by gains of chromosome 17q. To evaluate the effect of CEP17 gains (CEP17>3 copies per tumor nucleus) on the expression of the HER2 gene, which is located on chromosome 17q12-21.32, we analyzed HER2 amplification and expression in breast carcinomas with and without CEP17 gains. We isolated tumor nuclei from frozen tissues of 37 breast carcinomas for analysis of the HER2 gene and CEP17 by fluorescence in situ hybridization. HER2 expression was detected by immunohistochemistry (IHC) performed on formalin-fixed, paraffin-embedded sections of the corresponding tumors. Tumors with amplified HER2 as determined by both HER2 copy number and HER2/CEP17 ratio were detected in 29.7% (11/37). CEP17 gains were significantly associated with HER2 amplification (P=0.005) but not associated with estrogen receptor status, tumor grade, and lymph node status (P>0.05). In contrast, HER2 amplification was significantly associated with estrogen receptor negativity (P=0.020) but not with tumor grade and lymph node status (P>0.05). IHC analysis was performed in 7 HER2-amplified tumors and all of these were IHC 3+, which were used as positive controls. Among HER2-non-amplified tumors with CEP17 gains, only 1 tumor (1/8, 12.5%) was IHC 3+. However, none of the HER2-non-amplified tumors without CEP17 gains was IHC 3+. In HER2-non-amplified tumors, there was no significant association between HER2 protein expression as detected by IHC and CEP17 or HER2 copy number (P=0.999, P=0.785, respectively). These findings indicate that in the absence of HER2 amplification, CEP17 gains do not have a significant effect on HER2 protein expression.

EGFR molecular profiling in advanced NSCLC: a prospective phase II study in molecularly/clinically selected patients pretreated with chemotherapy

INTRODUCTION

The optimal use of epidermal growth factor receptor (EGFR)-related molecular markers to prospectively identify tyrosine kinase inhibitor (TKI)-sensitive patients, particularly after a previous chemotherapy treatment, is currently under debate.

METHODS

We designed a prospective phase II study to evaluate the activity of EGFR-TKI in four different patient groups, according to the combination of molecular (EGFR gene mutations, EGFR gene copy number and protein expression, and phosphorylated AKT expression, pAKT) and clinicopathological (histology and smoking habits) factors. Correlations between molecular alterations and clinical outcome were also explored retrospectively for first-line chemotherapy and EGFR-TKI treatment.

RESULTS

Patients who had progressed during or after first-line chemotherapy were prospectively assigned to EGFR-TKI treatment as follows: (G1) EGFR mutation (n = 12); (G2) highly polysomic/amplified EGFR (n = 18); (G3) EGFR and/or pAKT positive (n = 41); (G4) adenocarcinoma/bronchoalveolar carcinoma and no smoking history (n = 15). G1 and G4 had the best and second-best overall response rate (25% and 20%, respectively), whereas the worst outcome was observed in G2 (ORR, 6%; p = 0.05). Disease control was highest in G1 and G4 (>50%) and lowest in G3 (<20%) (p = 0.02). Patients selected by EGFR mutation or clinical parameters (G1 and G4) also had significantly better progression-free survival and overall survival (p = 0.02 and p = 0.01, respectively). Multivariate analysis confirmed the impact of sex, smoking history, EGFR/KRAS mutation, and pAKT on outcomes and allowed us to derive an efficient predictive model. Histology, EGFR mutations, and pAKT were independent predictors of response to first-line chemotherapy at retrospective analysis, whereas pAKT and human epidermal growth factor receptor 2 expression were the only independent predictors of progression-free survival and overall survival.

CONCLUSIONS

Selection of patients based on either EGFR mutation or clinical characteristics seems an effective approach to optimize EGFR-TKI treatment in chemotherapy-pretreated non-small-cell lung cancer patients.

Prognostic value of TOP2A gene amplification and chromosome 17 polysomy in early breast cancer

The aim of this study was to analyze the occurrence of TOP2A gene amplification and chromosome 17 polysomy in patients with early breast cancer and to correlate the status of these alterations with the prognostic significance expressed as patients' clinical features and survival. Such concurrent analyses of TOP2A gene status and chromosome 17 polysomy have not been performed before. Study group included 149 consecutive stage I-III patients administered standard multimodality treatment. TOP2A abnormalities were examined by standard fluorescence in situ hybridization (FISH) and developed by our group quantitative real-time PCR (qPCR). TOP2A amplification and deletion assessed by FISH were found in 23% and 7% of the tumours, respectively, and by qPCR in 31% and 11% of the tumours, respectively. Chromosome 17 polysomy was detected in 40% of the cases. TOP2A amplification (by qPCR) correlated with shorter disease-free survival (p = 0.03) and overall survival (p = 0.047), and the prognostic value of TOP2A was confirmed in the multivariate analysis (HR = 3.22, 95% CI 1.09-9.56, p = 0.03). TOP2A gene amplification, but not chromosome 17 polysomy, carries negative prognostic information in early breast cancer. Given the aforementioned results, qPCR might serve as a prognostic tool in determining the patient's prognosis.

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.

HER2 gene amplification in patients with breast cancer with equivocal IHC results

Aims

Equivocal human epidermal growth factor receptor 2 protein (HER2) (2+) immunohistochemistry (IHC) is subject to significant interobserver variation and poses a challenge in obtaining a definitive positive or negative test result. This equivocal test result group accounts for approximately 15% of all tumours, and for optimal guidance of HER2 targeted therapy, a further analysis of quantification of gene copy number and amplification status is needed for patients with early or metastatic breast cancer.

Methods

553 breast-cancer specimens with equivocal HER2 IHC(2+) test results were collected and subsequently centrally retested by chromogenic in situ hybridisation (CISH), and HER2 gene copy numbers per tumour cell nucleus were determined.

Results

Using CISH, 77 of 553 equivocal HER2 IHC(2+) test result cases (13.9% of total) showed high levels of HER2 gene amplification (≥10.0 gene copies per nucleus), and 41 of 553 (7.4% of total) showed low-level HER2 gene amplification (6.0–9.9 gene copies per nucleus). In 73.6% of cases, no amplification of the HER2 gene was shown, and in only 4.9% of cases was an equivocal test result by CISH observed (4.0–5.9 gene copies per nucleus).

Conclusions

Testing by CISH of all equivocal HER2 IHC(2+) test result provides a definitive guidance in HER2 targeted therapy in 95.1% of cases. A significant proportion (21.3%) of patients with equivocal IHC(2+) test results show amplification of the HER2 gene.

Chromosome 17 polysomy in circulating tumor cells in patients with metastatic breast cancer: a case series

The human epidermal growth factor receptor 2 (HER2) gene is located on the long arm of chromosome 17 (Chr-17). While primary tumors with Chr-17 polysomy (polysomy 17) are histopathologically similar to HER2-negative tumors, the role of polysomy 17 in circulating tumor cells (CTCs) is still unknown. We report the detection rate of polysomy 17 in CTCs in patients with metastatic breast cancer (MBC). We determined the CTC count per 7.5 ml blood and polysomy 17 in CTCs at 3- to 4-week intervals up to 12 weeks in 52 patients. Polysomy was defined as Chr-17 ≥2.2. CTCs were detected in 40 of 52 patients (76.9%) during the study period, in 32 of the 52 patients (61.5%) at baseline, and in 21 of 49 patients (42.9%) at 3-4 weeks. Polysomy 17 in CTCs was present in 10 of 52 patients (19.2%) during the study period, in 5 of 52 patients (9.6%) at baseline, and in 7 of 49 patients (14.3%) at 3-4 weeks. The individual patient counts of polysomy 17 in CTCs/total count of CTCs examined for polysomy 17 at 3-4 weeks were 1/1, 1/7, 1/7, 2/27, 2/30, 2/50, and 3/50. Six of the 7 patients with polysomy 17 in CTCs had HER2-negative primary tumors. None of the CTCs displaying polysomy 17 themselves had HER2 amplification by FISH. In summary, polysomy 17 in CTCs was observed in only a small population of patients with MBC. We should prospectively evaluate its prognostic value in both HER2-positive and -negative metastatic breast cancer.

Assessment of HER2 gene status in breast carcinomas with polysomy of chromosome 17

BACKGROUND

The current study was performed to determine the impact of polysomy 17 on the interpretation of HER2 testing of invasive breast carcinomas using fluorescent in situ hybridization methods. Current American Society of Clinical Oncology/College of American Pathologists guidelines define HER2-positive tumors as those with >6 HER2 genes per nucleus or those with HER2/CEP17 (chromosome 17) ratio >2.2. These guidelines are potentially contradictory in tumors with polysomy of chromosome 17.

METHODS

Seventy-two breast carcinoma cases with reported polysomy of chromosome 17 (≥ 3 CEP17 signals on average) by fluorescent in situ hybridization were identified, and the corresponding HER2 immunohistochemistry was obtained. The HER2 status of the archived samples was reviewed, and the tumors were recategorized according to the 2007 American Society of Clinical Oncology/College of American Pathologists guidelines.

RESULTS

The average CEP17 copy number for the group was 4.5 (range, 3.0-10.4). Thirty-three (45.8%) cases had >6 copies of HER2 per nucleus. Twenty-one cases (29.2%) qualified as HER2 gene amplified using the HER2/CEP17 ratio (>2.2) guideline. All these cases had >6 HER2 signals, which represented 63.6% of all cases with >6 HER2 signals. HER2 protein expression showed significant positive correlations with both HER2 gene copy number and HER2/CEP17 ratio (P < .01, r(s) = 0.56 and 0.64, respectively).

CONCLUSIONS

Increased CEP17 signals detected in invasive breast carcinomas may lead to discordant interpretation of gene amplification in a significant proportion of the cases, depending on which criterion (ratio vs absolute number) is used for interpretation. However, increased gene dosage (>6 HER2 genes or HER2/CEP17 ratio >2.2), regardless of the evaluation method, is positively correlated with HER2 protein expression.

Human epidermal growth factor receptor 2 assessment in a case-control study: comparison of fluorescence in situ hybridization and quantitative reverse transcription polymerase chain reaction performed by central laboratories

PURPOSE

The optimal method to assess human epidermal growth factor receptor 2 (HER2) status remains highly controversial. Before reporting patient HER2 results, American Society of Clinical Oncology (ASCO)/College of American Pathologists (CAP) guidelines mandate that laboratories demonstrate ≥ 95% concordance to another approved laboratory or methodology. Here, we compare central laboratory HER2 assessed by fluorescence in situ hybridization (FISH) and quantitative reverse transcriptase polymerase chain reaction (RT-PCR) using Oncotype DX in lymph node-negative, chemotherapy-untreated patients from a large Kaiser Permanente case-control study.

PATIENTS AND METHODS

Breast cancer specimens from the Kaiser-Genomic Health study were examined. Central FISH assessment of HER2 amplification and polysomy 17 was conducted by PhenoPath Laboratories (ratios > 2.2, 1.8 to 2.2, and < 1.8 define HER2 positive, HER2 equivocal, and HER2 negative, respectively). HER2 expression by RT-PCR was conducted using Oncotype DX by Genomic Health (normalized expression units ≥ 11.5, 10.7 to < 11.5, and < 10.7 define HER2 positive, HER2 equivocal, and HER2 negative, respectively). Concordance analyses followed ASCO/CAP guidelines.

RESULTS

HER2 concordance by central FISH and central RT-PCR was 97% (95% CI, 96% to 99%). Twelve percent (67 of 568 patients) and 11% (60 of 568 patients) of patients were HER2 positive by RT-PCR and FISH, respectively. HER2-positive patients had increased odds of dying from breast cancer compared with HER2-negative patients. Polysomy 17 was demonstrated in 12.5% of all patients and 33% of FISH-positive patients. Nineteen of 20 FISH-positive patients with polysomy 17 were also RT-PCR HER2 positive. Although not statistically significantly different, HER2-positive/polysomy 17 patients tended to have the worst prognosis, followed by HER2-positive/eusomic, HER2-negative/polysomy 17, and HER2-negative/eusomic patients.

CONCLUSION

There is a high degree of concordance between central FISH and quantitative RT-PCR using Oncotype DX for HER2 status, and the assay warrants additional study in a trastuzumab-treated population.

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.

Breast cancer and aneusomy 17: implications for carcinogenesis and therapeutic response

Abnormalities of chromosome 17, recognised over two decades ago to be important in tumorigenesis, often occur in breast cancer. Changes of specific loci on chromosome 17 including ERBB2 amplification, P53 loss, BRCA1 loss, and TOP2A amplification or deletion are known to have important roles in breast-cancer pathophysiology. Numerical aberrations of chromosome 17 are linked to breast-cancer initiation and progression, and possibly to treatment response. However, the clinical importance of chromosome 17 anomalies, in particular the effect on ERBB2 protein expression, is unknown. Reports are conflicting regarding the association of copy gain of chromosome 17 (polysomy 17) with strong ERBB2 protein expression in the absence of true ERBB2 gene amplification. Copy-number anomalies in chromosome 17 seem to be common in tumours that show discrepant ERBB2 expression and in tumours with discordant ERBB2-protein and ERBB2 gene copy number measurements. The mechanisms of ERBB2 dosage changes-gene amplification versus chromosome gain and loss-probably differ in primary and metastatic disease; however, a correction for chromosome 17 copy-number is necessary to completely distinguish between these mechanisms. A better understanding of how polysomy 17 affects gene-copy number and protein expression will help to select patients who will respond to therapies targeting ERBB2 and other protein products of chromosome 17 loci.

Prediction of HER2 gene status in Her2 2+ invasive breast cancer: a study of 108 cases comparing ASCO/CAP and FDA recommendations

Most Her2 testing guidelines recommend that all cases scoring Her2 2+ by immunohistochemistry should be analyzed by fluorescent in situ hybridization (FISH) to determine HER2 status to confirm eligibility for Trastuzumab therapy in breast cancer. The aim of our study was to determine HER2 gene and chromosome 17 (CEN17) status in a series of 108 Her2 2+ consecutive cases and study the correlation between pathological characteristics of the tumors and HER2 amplification. Invasive breast cancers were tested by FISH using the Dako HER2 FISH pharmDx kit. The Her2 immunohistochemistry protocol was performed using the polyclonal AO485 antibody (Dako) diluted to 1:1500. HER2 and CEN17 status were correlated to tumor SBR grade, mitotic count, estrogen receptor, progesterone receptor status and percentage of Her2 immunohistochemistry-positive cells. Following Food and Drug Administration guidelines, ie, HER2/CEN17 ratio >or=2 and an HER2 copy number >4, amplified cases were observed in 36 (33%) and 49 (45%) cases, respectively, and following American Society of Clinical Oncology/College of American Pathologists guidelines, ie, HER2/CEN17 ratio >2.2 and an HER2 copy number >6, amplified cases represented 30 and 24% of the study population, respectively. Chromosome 17 polysomy (CEN17 >2.25) was observed in 39 (36%) tumors. Significant positive correlations were found between FISH HER2 amplified cases and Her2 immunostaining >60% (P=1.1.10(-5)), SBR grade 3 (P=0.0001), nuclear atypia (P=0.03) and mitotic count (P=0.008). By multivariate analysis, Her2 immunostaining >60% (P<10(-3)) and SBR grade 3 (P<10(-3)) were independent factors predicting HER2 amplification status irrespective to cutoff guidelines. All SBR grade 3 cases with more than 60% Her2+ cells had an HER2/CEN17 ratio >or=2, only one had a ratio <or=2.2. In our series of consecutive Her2 2+ cases, one-third demonstrated HER2 amplification, and one-third had chromosome 17 polysomy. Pathological factors, in particular SBR grade 3 and more than 60% Her2+ cells, were significantly correlated with HER2 amplification.

Polysomy 17 in breast cancer: clinicopathologic significance and impact on HER-2 testing

PURPOSE

Polysomy 17 is frequently found in breast cancer and may complicate the interpretation of HER-2 testing results. We investigated the impact of polysomy 17 on HER-2 testing and studied its clinicopathologic significance in relation to HER2 gene amplification.

PATIENTS AND METHODS

In 226 patients with primary invasive breast carcinoma, HER2 gene and chromosome 17 copy numbers were determined by dual-color fluorescent in situ hybridization (FISH). The interpretation of FISH results was based on either absolute HER2 gene copy number or the ratio HER2/chromosome 17. Results were correlated with HER-2 protein expression on immunohistochemistry (IHC), HER2 mRNA expression by reverse transcriptase polymerase chain reaction (RT-PCR), and with various clinicopathologic parameters.

RESULTS

All cases with an equivocal HER-2 result by FISH, either by absolute HER2 copy number (44 of 226 patients; 19.5%) or by the ratio HER2/chromosome 17 (three of 226 patients; 1.3%), displayed polysomy 17. On its own, polysomy 17 was not associated with HER-2 overexpression on IHC or increased HER2 mRNA levels by RT-PCR. Moreover, and in contrast with HER2 gene amplification, polysomy 17 was not associated with high tumor grade, hormone receptor negativity, or reduced disease-free survival.

CONCLUSION

Polysomy 17 affects HER-2 testing in breast cancer and is a major cause of equivocal results by FISH. We show that tumors displaying polysomy 17 in the absence of HER2 gene amplification resemble more HER-2-negative than HER-2-positive tumors. These findings highlight the need for clinical trials to investigative whether polysomy 17 tumors benefit from HER-2-targeted therapy.

EGFR/HER2 in breast cancer: a biological approach for molecular diagnosis and therapy

Novel cancer therapies have focused on specific molecular markers present in malignant tumors. The rationale of targeted therapy relies on the knowledge of molecular mechanisms involved in carcinogenesis and their influence in clinical outcome allied to a more specific and less toxic treatment. Activation of EGF receptor and HER2 is an important factor for initiation and progression of malignancies, including breast cancer where the status of HER2 is an essential step in the diagnostic workup; EGFR overexpression has been associated to the so-called basal-like breast carcinomas, which opens a new avenue for diagnosis and therapeutic approach in these tumors. This review will focus on mechanisms of HER2 and EGF receptor upregulation, the targeted therapies that are currently in use for these receptors, possible combined therapies, as well as the approach for molecular diagnosis from the pathologist's point of view.

The complexity of genotypic alterations underlying HER2-positive breast cancer: an explanation for its clinical heterogeneity

PURPOSE OF REVIEW

We discuss recent findings on the genotypic alterations associated with HER2-positive breast cancer in an attempt to clarify the clinical heterogeneity observed among these tumors.

RECENT FINDINGS

Molecular genetic analysis supports the distinctive nature of HER2-positive breast cancer, which is primarily driven by HER2 gene amplification. Depending on the amplicon size, a variety of genes can be coamplified and overexpressed together with HER2, some of which may contribute to tumorigenesis; the amplicon size may even predict response to trastuzumab therapy. HER2 gene amplification may further destabilize the tumor genome, facilitating the generation of additional genomic aberrations including aneuploidy. The latter might imply polysomy 17, a phenomenon that should be discriminated from true HER2 gene amplification: polysomy 17 in the absence of HER2 gene amplification is not associated with HER2 overexpression nor with the clinical characteristics of HER2-positive breast cancer.

SUMMARY

HER2 gene amplification is a complex event: it includes coamplification of other, potentially oncogenic genes and facilitates the generation of additional genomic aberrations. Further studies on these genotypic findings will be helpful to better identify the patients that might benefit from trastuzumab therapy.

Comparative evaluation of non-informative HER-2 immunoreactions (2+) in breast carcinomas with FISH, CISH and QRT-PCR

The routine assessment of HER-2 expression can be affected by many immunohistological preanalytical and analytical variables. The evaluation of non-informative HER-2 tests, because of 2(+) scores, has been addressed in studies using in situ hybridization (fluorescent in situ hybridization (FISH) or chromogenic in situ hybridization (CISH)). There are very few studies that additionally checked 2(+) cases by quantitative reverse transcription-PCR (QRT-PCR). We analyzed totally 195 breast carcinoma cases, 70 of them showing 2(+) immunoreaction, with FISH/CISH and QRT-PCR. Confirmed amplification in 2(+) cases fell within the reported range (12.8% vs. 8-44%) and some of them showed lower mRNA levels indicating a genuine decrease of HER-2 protein as a mechanism for the non-informative score. In other cases, increased mRNA levels could be ascribed to HER-2 polysomy, verifying previous observations of immunohistologically detectable HER-2 polysomy. A remarkable subset of the 2(+) cases showed "normal" mRNA levels without amplification or polysomy and technical parameters as well as heterogeneity could be incriminated. The overall concordance of QRT-PCR and FISH was 93.8%, highest than most previously reported. Yet, the lack of clear cut-off mRNA values and the challenge of sample microdissection hinder QRT-PCR from claiming the status of a gold standard test for HER-2 evaluation.

HER2 status in early breast cancer: relevance of cell staining patterns, gene amplification and polysomy 17

The prevalence of HER2 amplification according to the percentage of positively stained cells, of polysomy 17 and their correlation with clinical and pathologic characteristics were retrospectively evaluated in a population of 415 breast cancers where fluorescence in situ hybridisation (FISH) was performed to clarify HER2 status previously determined by immunohistochemistry. Forty-two tumours with intense and complete staining in >50% of cells were selected from the same database as internal controls. Among the 415 cases, 233 tumours were IHC 1+, 168 tumours were 2+ and 14 tumours showed an intense and complete immunostaining in 50% of neoplastic cells. HER2 was amplified in 3/14 (21.4%) tumours with 50% and in 36/42 (85.7%) tumours with >50% of intense stained cells, (p<0.001). Polysomy 17 was detected in 77 tumours (16.85%). It was inversely correlated with the percentage of positively stained cells, but not with amplification. Patients with polysomy 17 and no amplification were significantly more likely to have tumours with favourable biological features when compared with patients with HER2 amplification. Our results suggest that FISH testing should be considered for tumours with 50% positive stained cells and that polysomy 17 without amplification is not associated with poor prognostic features.

Chromogenic and fluorescent in situ hybridization in breast cancer

Fluorescent (FISH) and chromogenic (CISH) in situ hybridization have recently become part of the diagnostic armamentarium of breast pathologists. HER2 gene testing by FISH and/or CISH has become an integral part of the diagnostic workup for patients with breast cancer. In this era of high throughput technologies, these techniques have proven instrumental for the validation of results from microarray-based comparative genomic hybridization and for the identification of novel oncogenes and tumor suppressor genes. Furthermore, FISH and CISH applied to tissue microarrays have expedited the characterization of genomic changes associated with specific breast cancer molecular subtypes and the identification of novel prognostic and predictive markers. In this review, we provide in this review a critical assessment of CISH and FISH and the impact of the analysis of amplification of specific oncogenes (eg, HER2, EGFR, MYC, CCND1, and FGFR1) and deletion of tumor suppressor genes (eg, BRCA1 and BRCA2) on our understanding of breast cancer.