Abstract: Objective To investigate the expression level and amplification condition of HER2 and TOP2A as well as their relationship in breast cancer. Methods Immunohistochemistry and fluorescent in situ hybridization (FISH) were taken to detect the the expression level of HER2/topoⅡα, amplification status of HER2 gene/TOP2A gene respectively. Statistical analysis was performed to explore the correlation between them. Results The breast cancer tissues of 58 patients were tested. The expression level of HER2 was investigated in 11 cases with negative expression（11/58,19.0%）,19 cases with weakly positive expression（19/58,32.8%），13 cases with positive expression（13/ 58,22.4%）and 15 cases with strongly positive expression（15/58,25.8%）. The expression level of topoⅡα was investigated in 28 cases with negative expression（28/58,48.3%），22 cases with positive expression（22/58,37.9%），8 cases with strongly expression（8/58,13.8%）. Amplification of HER2 and TOP2A gene was detected in 19 patients（19/58,32.8%）, 11 patients（11/58,19.0%）respectively. Non-amplification of HER2 gene and TOP2A was detected in 39 patients （39/58,67.2%）, 47 patients（47/58,81.0%）respcetively. Spearman rank correlation analysis revealed that the expression level of HER2 protein was significantly related with the amplification status of HER2 gene (EM>rSUB>s/SUB>/EM>=0.80,EM>P/EM><0.05）and the expressio

Key words: Breast cancer, HER2, TOP2A, Immunohistochemistry, Fluorescent EM>in situ/EM> hybridization, Human