Quality control for histological grading in breast cancer: an Italian experience

Although the diagnostic criteria for histological grading in breast cancer have been improved by the introduction of the Nottingham/Tenovus classification, good results in terms of reproducibility are hard to obtain. The objective of this study was to validate a methodological protocol for external quality control. We assessed the intra- and interlaboratory reproducibility for grading score and its components. Our findings revealed a less than optimal level of agreement for both intra-observer and interobserver reproducibility. Each grading class contributed in a different way to the reproducibility and class G2 provided the poorest contribution to the observed agreement. Nuclear pleomorphism appeared to be the least reproducible, followed by mitotic count and tubule formation. In conclusion, our results suggest the need for quality control programs that should be conceived as a dynamic feedback process to better understand the reasons for some unsatisfactory performances and to implement the necessary corrective actions.