Abstract
Human epidermal growth factor receptor 2 (HER2) amplification and overexpression are associated with poor prognosis and resistance to cytotoxic drugs in patients with breast cancer. Increases in the number of HER2 gene copies have been shown to be associated with chromosome 17 polysomy. The use of whole, intact nuclei for fluorescence in situ hybridization (FISH) assay improves the accuracy of the results. FISH analysis of whole nuclei (WNFISH) and immunohistochemistry (IHC) were used to analyze HER2 gene amplification and HER2 protein expression in 109 breast cancer specimens. Chromosome 17 polysomy and its correlations with HER2 gene amplification, HER2 protein expression and the clinicopathological outcomes of the patients were also investigated. Among the 109 cases, WNFISH detected HER2 amplification in 30 cases, equivocal amplification in 19 cases and no amplification in 60 cases. WNFISH detected chromosome 17 centromere (CEP17) polysomy in 37 cases and no polysomy in 72 cases. Among the 109 cases assessed by tissue microarray and IHC, 31 cases were HER2-negative, 14 cases were scored 1+, 23 cases were scored 2+ and 41 cases were scored 3+. The results demonstrated that in the cases with chromosome 17 polysomy, the HER2 gene was amplified, HER2 protein expression was increased and the incidences of nuclear atypia and lymph node metastases were higher compared with those in the cases without chromosome 17 polysomy. Chromosome 17 polysomy may correlate with increased malignant potential and metastatic spread in breast cancer.
Highlights
Breast cancer is one of the common types of cancer in females
The CEP17 and human epidermal growth factor receptor 2 (HER2) statuses evaluated by WNFISH were available for all 109 samples
75% of chromosome 17 polysomy cases were accompanied by HER2 gene amplification
Summary
Breast cancer is one of the common types of cancer in females. The incidence of breast cancer increases each year, and the proportion of affected young females increases, posing a serious threat to the health of the population [1]. For the assessment of the HER2 gene copy number, it has been suggested that systems assessing the HER2/chromosome 17 centromere (CEP17) ratio, such as dual‐ or single‐color fluorescence in situ hybridization (FISH) or chromogenic in situ hybridization (CISH), provide a more accurate evaluation of HER2 amplification than single‐probe systems. These methods have successfully identified patients who will benefit from trastuzumab therapy in clinical trials [5]. 8% of breast cancers exhibit increased copy numbers of CEP17 using FISH (i.e., average CEP17 >3.0 per nucleus), and these cancers possess chromosome 17 polysomy [3,6,7]
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