[Automated silver-enhanced in situ hybridization detection assay for human epidermal growth factor receptor 2 gene status determination in breast cancer].

OBJECTIVE: To evaluate the concordance of human epidermal growth factor receptor 2 (HER2) gene amplification in invasive breast cancer by the techniques of fluorescence in situ hybridization (FISH) and silver-enhanced in situ hybridization (SISH). METHODS: A prospective study of 63 invasive breast cancer specimens excised between May 2009 and November 2009 was conducted by automated immunohistochemistry (IHC) staining and bright field automated SISH. HER2 gene status was also examined by FISH in 43 cases. An evaluation was performed according to the ASCO/CAP guidelines (2007). RESULTS: Among 63 breast invasive ductal carcinoma tested by automated SISH, 61 cases were successfully evaluated. Gene amplification was detected in 97% (29/30) HER2 protein expression positive (3+) cases and in 18% (2/11) equivocal (2+) cases. Two of 11 (18%) HER2 expression 2+ cases were equivocal for gene amplification. In 43 cases examined by FISH, HER2 gene amplification was detected in 95% (20/21) HER2 expression positive (3+) cases and in one equivocal (2+) cases. Three of 10 (30%) expression 2+ cases were equivocal for gene amplification. No gene amplification was detected in expression negative (1 +/0) cases by either SISH or FISH (0/20 and 0/12 respectively). The results of SISH and FISH were identical in 42 cases examined by the above two techniques, including 21 HER2 gene amplification positive, 2 equivocal and 19 negative cases. One case was FISH equivocal and SISH negative. And the overall concordance between FISH and SISH was 98%. CONCLUSIONS: There is high concordance rate between SISH and FISH results for assessing the HER2 gene amplification status of excised breast cancer specimens. However, SISH has more advantages and it is particularly suited for routine application in surgical pathology.