An Intra- and Interobserver Reproducibility Analysis of the Ki-67 Proliferation Marker Assessment on Core Biopsies of Breast Cancer Patients and Its Potential Clinical Implications

Abstract

Our results indicate that the three different Ki-67 antibodies tested do not substantially influence the reproducibility of the estimated proliferation rates. Although reproducibility is better in the clinically more relevant distinction of high versus low proliferation, without standardization, the current practice of Ki-67 assessment in many laboratories does not allow proper and consistent therapeutic decision-making.