The International Ki67 Working Group has focused on the major source of identified inter-laboratory variability: differences in scoring interpretation. Our group has not yet completed planned studies assessing specific contributions to analytical variability from staining methodologies. Currently, we recommend guidelines for staining as previously published based on a review of the literature . In particular, pre-analytical handling of breast cancers should follow ASCO/CAP guidelines for ER and HER2 testing, which is sufficient to maintain Ki67 antigenicity.
- Dowsett M, Nielsen TO, A’Hern R et al. Assessment of Ki67 in breast cancer: recommendations from the International Ki67 in Breast Cancer Working Group. J Natl Cancer Inst 2011;103:1656–1664.”