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Expression, assessment and significance of Ki67 expression in breast cancer: an update
  1. Ayat Gamal Lashen1,2,
  2. Michael S Toss1,3,
  3. Suzan Fathy Ghannam1,4,
  4. Shorouk Makhlouf1,5,
  5. Andrew Green1,6,
  6. Nigel P Mongan7,8,
  7. Emad Rakha1,2,9
  1. 1 Academic Unit for Translational Medical Sciences, School of Medicine, University of Nottingham, Nottingham, UK
  2. 2 Department of Pathology, Faculty of Medicine, Menoufia University, Shebin El Kom, Egypt
  3. 3 Department of pathology, Sheffield Teaching Hospitals NHS Foundation Trust, Sheffield, UK
  4. 4 Department of Histology, Suez Canal University, Ismailia, Egypt
  5. 5 Department of Pathology, Faculty of Medicine, Assiut University, Assiut, Egypt
  6. 6 Nottingham Breast Cancer Research Centre, University of Nottingham, Nottingham, UK
  7. 7 School of Veterinary Medicine and Sciences, University of Nottingham, Nottingham, UK
  8. 8 Department of Pharmacology, Weill Cornell Medicine, New York, New York, USA
  9. 9 Pathology Department, Hamad Medical Corporation, Doha, Qatar
  1. Correspondence to Professor Emad Rakha, Pathology Department, Hamad Medical Corporation, Doha, Qatar; emad.rakha{at}


Ki67 expression is one of the most important and cost-effective surrogate markers to assess for tumour cell proliferation in breast cancer (BC). The Ki67 labelling index has prognostic and predictive value in patients with early-stage BC, particularly in the hormone receptor-positive, HER2 (human epidermal growth factor receptor 2)-negative (luminal) tumours. However, many challenges exist in using Ki67 in routine clinical practice and it is still not universally used in the clinical setting. Addressing these challenges can potentially improve the clinical utility of Ki67 in BC. In this article, we review the function, immunohistochemical (IHC) expression, methods for scoring and interpretation of results as well as address several challenges of Ki67 assessment in BC. The prodigious attention associated with use of Ki67 IHC as a prognostic marker in BC resulted in high expectation and overestimation of its performance. However, the realisation of some pitfalls and disadvantages, which are expected with any similar markers, resulted in an increasing criticism of its clinical use. It is time to consider a pragmatic approach and weigh the benefits against the weaknesses and identify factors to achieve the best clinical utility. Here we highlight the strengths of its performance and provide some insights to overcome the existing challenges.

  • breast
  • breast neoplasms
  • neoplasm metastasis

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  • Handling editor L C Collins.

  • Contributors ER and AGL designed the article. AGL wrote the manuscript. ER, MST, NPM, AG, SFAG and SM critically reviewed the article.

  • Funding AGL is supported and funded by the Egyptian Ministry of Higher Education and Scientific Research.

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.