HER2 overexpression of breast cancers in Hong Kong shows good concordance with HER2 amplification by fluorescence in-situ hybridisation study.

Our results, from tests performed at Queen Elizabeth Hospital, Hong Kong, are different. Of 260 consecutive invasive breast cancers, 57.3% scored 0 or 1 (negative) on HER2 immunostaining , 26.2% scored 2 (borderline) and 16.5% scored 3 (strong), results comparable to those reported in the literature.2 Our correlation study using the fluorescence ISH test for HER2 amplification (PathVysion Kit) shows HER2 amplification in none of the 10 negative cases (score 0 or 1), four (6.9%) of 58 score 2 cases, and 12 (92.3%) of 13 score 3 cases. The single negative score 3 case showed increased copies of HER2 gene, but since there was also chromosome 17 polysomy, the ratio of HER2/CEP17 fell below 2.2 (negative by definition). The good concordance between strong HER2 overexpression with HER2 amplification supports the general recommendation that breast cancers with score 3 HER2 overexpression do not require molecular confirmation. The differences between our results and those reported by Yau et al may be due to their inclusion of results from different laboratories, using different antibodies and different technologies.