Tissue microarray technology in the routine assessment of HER-2 status in invasive breast cancer:: a prospective study of the use of immunohistochemistry and fluorescence in situ hybridization

Aims: To compare tissue microarray (TMA) and whole-section (WS) techniques in the routine assessment of HER-2 status in invasive breast cancer by immunohistochemistry and fluorescence in situ hybridization (FISH). Methods and results: HER-2 status was assessed prospectively in 106 consecutive cases of excised high-grade and/or node-positive breast carcinoma using both WS- and TMA-based techniques. Whole sections were assessed by immunohistochemistry with FISH being performed on equivocal cases (scoring 2+ on Hercep (R) Test) and randomly selected 3+ cases included for quality assurance. Five 0.6-mm cores from each tumour allowed accurate immunohistochemical and FISH testing in > 95% of cases. Ninety-seven per cent concordance was achieved between WS and TMA approaches to FISH analysis, the only discrepancies being in cases that were borderline or near borderline by both techniques. TMA and WS approaches were comparable in terms of time for preparation and scoring. Conclusions: TMA technology is a robust method of assessing HER-2 status in invasive breast cancer. This is directly comparable to the current standard methodology using whole sections. The use of TMA technology offers several advantages over existing full-section methods in terms of cost, quality control, facilitation of future research and the facility to provide a high-throughput testing methodology.