The effect of an alternative chromosome 17 probe on fluorescence in situ hybridization for the assessment of HER2 amplification in invasive breast cancer

Fluorescent in situ hybridization (FISH) is commonly used to determine the ratio of human epidermal growth factor receptor 2 (HER2) to centromere enumeration probe for chromosome 17 (CEP17), which further determines HER2 gene status in breast cancer. However, due to copy number alteration in CEP17, inaccurate diagnoses can occur. The current study was performed to investigate the diagnostic value of an alternative CEP17 reference probe for HER2 status in invasive breast cancer. A higher-order repeat in the centromeric region of chromosome 17 was identified and an alternative probe (SCEP17) was subsequently prepared. Karyotype analysis of peripheral blood was used to detect SCEP17 probe specificity. Using a HER2/CEP17 probe, karyotype analysis revealed two strong green signals at the centromere of chromosome 17 and one weaker signal at the other centromere. However, two strong hybridization signals at the centromere of chromosome 17 were observed when the HER2/SCEP17 probe was used. In the 425 patients with invasive breast cancer, no statistical difference was observed between HER2/SCEP17 and HER2/CEP17 when detecting HER2 gene amplification (P=0.157). However, in terms of copy number, the SCEP17 probe exhibited a reduced number compared with the conventional CEP17 probe (P<0.001). In conclusion, the HER2/SCEP17 probe may lead to increased accuracy HER2 status assessment in invasive breast cancer. However, a further large-scale and prospective clinical trial is required for confirmation of the potential benefits of using the HER2/SCEP17 probe.