Immunohistochemical HER2 Status Evaluation in Breast Cancer Pathology Samples: A Multicenter, Parallel-Design Concordance Study

Objective As patients with increased human epidermal growth factor receptor (HER2) overexpression are more likely to benefit from trastuzumab treatment, the accuracy of HER2 receptor status in breast cancer patients is significant for appropriate disease management. However, this assessment is not harmonized and results may be highly variable between centers. The aim of this study was to investigate the degree of interlaboratory variability in the results of HER2 expression reported by 5 participating centers and to assess the concordance between these centers and a reference laboratory. Materials and Methods: A total of 30 breast cancer samples were tested and scored for HER2 expression using immunohistochemical method in 5 centers from Turkey and in a reference laboratory from Netherlands (Academic Medical Center, Amsterdam). All the participating centers had an experience of more than 10 years regarding the HER2 testing. The results were compared both among the centers and with the reference laboratory.