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

Abstract

OBJECTIVE: : 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. RESULTS: When the concordance of participating centers and the reference laboratory was evaluated regarding negative (0-1+), equivocal 2(+) and positive 3(+) classification of HER2 immunostaining, the highest concordance was found in Center-A, and the lowest in Center-C (Kendall's tau-b concordance coefficient 0.911 and 0.724, respectively). The concordance of the centers with reference laboratory was 80.0% both in equivocal and positive samples, while it increased up to 91.8% in negative samples. CONCLUSIONS: This study showed that in general there is sufficiently good agreement between the reference laboratory and the participating centers for immunohistochemical HER2 assessment.