Analytical validation of a standardized scoring protocol for Ki67 immunohistochemistry on breast cancer excision whole sections: an international multicenter collaboration

Research output: Contribution to journalArticle


Aims: The nuclear proliferation marker Ki67 assayed by immunohistochemistry has multiple potential uses in breast cancer, but an unacceptable level of interlaboratory variability has hampered its clinical utility. The International Ki67 in Breast Cancer Working Group has undertaken a systematic programme to determine whether Ki67 measurement can be analytically validated and standardised among laboratories. This study addresses whether acceptable scoring reproducibility can be achieved on excision whole sections.

Methods and results: Adjacent sections from 30 primary ER+ breast cancers were centrally stained for Ki67 and sections were circulated among 23 pathologists in 12 countries. All pathologists scored Ki67 by two methods: (i) global: four fields of 100 tumour cells each were selected to reflect observed heterogeneity in nuclear staining; (ii) hot‐spot: the field with highest apparent Ki67 index was selected and up to 500 cells scored. The intraclass correlation coefficient (ICC) for the global method [confidence interval (CI) = 0.87; 95% CI = 0.799–0.93] marginally met the prespecified success criterion (lower 95% CI ≥ 0.8), while the ICC for the hot‐spot method (0.83; 95% CI = 0.74–0.90) did not. Visually, interobserver concordance in location of selected hot‐spots varies between cases. The median times for scoring were 9 and 6 min for global and hot‐spot methods, respectively.

Conclusions: The global scoring method demonstrates adequate reproducibility to warrant next steps towards evaluation for technical and clinical validity in appropriate cohorts of cases. The time taken for scoring by either method is practical using counting software we are making publicly available. Establishment of external quality assessment schemes is likely to improve the reproducibility between laboratories further.


  • Samuel CY Leung
  • Torsten Nielsen
  • Lila A Zabaglo
  • Indu Arun
  • Sunil S Badve
  • Anita L Bane
  • John Bartlett
  • Martin C Chang
  • A Dodson
  • Susan Fineberg
  • Cornelia Focke
  • Dongxia Gao
  • Allen M Gown
  • Carolina Gutierrez
  • Judith C Hugh
  • Zuzana Kos
  • Anne Vibeke Laenkholm
  • Mauro G Mastropasqua
  • Takuya Moriya
  • Sharon Nofech-Mozes
  • C Kent Osborne
  • Frédérique M Penault-Llorca
  • Tammy Piper
  • Takashi Sakatani
  • Roberto Salgado
  • Jane Starczynski
  • Tomoharu Sugie
  • Bert van der Vegt
  • Giuseppe Viale
  • Daniel Hayes
  • Lisa M McShane
  • Mitch Dowsett
External organisations
  • Institute of Cancer Research London
  • University of British Columbia
  • McMaster University
  • Indiana University
  • Ontario Institute for Cancer Research
  • Western General Hospital
  • University of Vermont
  • Dietrich-Bonhoeffer-Klinikum
  • Breast International Group
  • The International Ki67 in Breast Cancer Working Group
  • Baylor College of Medicine
  • University of Alberta
  • University of Ottawa
  • The Ottawa Hospital
  • University College Zealand
  • Slagelse Hospital
  • European Institute of Oncology
  • Kawasaki Medical School
  • Sunnybrook Health Sciences Centre
  • University of Auvergne
  • Nippon Medical School
  • Birmingham Heartlands Hospital
  • University Medical Center Groningen
  • University of Milan
  • University of Michigan
  • National Cancer Institute, NCI
  • University of Antwerp
  • Tata Medical Center, Kolkata
  • Skåne University Hospital
  • PhenoPath Laboratories, Seattle
  • Peter MacCallum Cancer Centre
  • Kansai Medical University
  • Royal Marsden Hospital
  • University of Vermont Medical Center (UVM)
  • University of Toronto
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Cancer and Oncology
Original languageEnglish
Pages (from-to)225-235
Number of pages11
Issue number2
Early online date2019 Apr 24
Publication statusPublished - 2019 Aug
Publication categoryResearch

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Ehinger, A. (Member), Borgquist, S. (Member)
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