Abstract: Objective： To study the evaluation of human epithelial growth factor receptor 2 (HER2) status in breast carcinoma with amplified chromosome 17 centromere locus (CEP17) and clinical significance of CEP17 amplification. Methods: Two hundred-eighteen cases of breast carcinoma were collected. We performed immunohistochemistry (IHC) to test HER2 protein and fluorescence in situ hybridization (FISH) to evaluate HER2 gene status. Results: Two cases in this cohort manifested CEP17 amplification. HER2 signals for case 1 was countable, and the average number was 2.6 per one nuclei, and the signals of CEP17 were clustered or multipunctiform. This case was evaluated as no HER2 amplification, but with amplified CEP17 . In case 2 the signals of HER2 and CEP17 were countable, and the average number of HER2 signal was 6.8 per one nucleus while CEP17 signal was 5.9 per one nucleus. The status was considered as HER2 and CEP17 coamplification. And the levels of HER2 protein expression of these two cases were both two plus. Conclusion： The incidence of CEP17 amplification in breast carcinoma is rare, with or without HER2 amplification. We recommend to evaluate the exact HER2 status by the HER2 copy number, and should also analyze the HER2/CEP17 ratio and the level of HER2 protein, for providing more accurate evidence to support the clinical target therapy.

Key words: Breast neoplasms, Gene, erbB-2, In situ hybridization, fluorescence, Centromere