c-erbB-2 (HER-2/neu) immunohistochemistry in invasive breast cancer: is there concordance between standard sections and tissue microarrays?

Aims: Immunohistochemical detection of the 185- kDa transmembrane glycoprotein product of the proto-oncogene cerbB2 ( also known as HER-2/ neu), located on chromosome 17q21, is a well established method of evaluation in invasive breast cancer. This investigation is currently performed on standard sections cut from the tumour containing paraffin block. It is uncertain if concordant results can be obtained on tissue microarray ( TMA) sections, a high throughput technique that is particularly advantageous in research and validation protocols. Our aim in this study was to compare the results of c-erbB-2 immunoexpression in standard sections of invasive breast cancers with those of TMAs. Methods: Standard sections and TMAs constructed from archival paraffin- embedded breast cancers of 184 patients who had surgery in Singapore General Hospital during the period 1998 - 2002 were subjected to immunohistochemistry using the commercial antibody (A0485, Dako). c-erbB-2 over- expression was evaluated according to cytoplasmic membrane staining intensity, which was defined as 2+ and 3+ staining. Results: Over-expression of c-erbB-2 protein was found in 21.2% (39/184) and 18.6% (34/183) of cases on standard sections and TMAs, respectively. There was substantial agreement between these two types of sections (k50.724) when positive and negative staining was considered. Conclusion: Immunohistochemistry on TMAs for c-erbB-2 expression in breast cancer is a reliable alternative to that performed on routine standard sections, as it is both cost effective and time efficient, especially in a research setting.