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Expression, assessment and significance of Ki67 expression in breast cancer: an update

Lashen, Ayat Gamal; Toss, Michael S; Ghannam, Suzan Fathy; Makhlouf, Shorouk; Green, Andrew; Mongan, Nigel P.; Rakha, Emad


Ayat Gamal Lashen

Michael S Toss

Suzan Fathy Ghannam

Shorouk Makhlouf

Professor of Oncology

Professor of Breast Cancer Pathology


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.


Lashen, A. G., Toss, M. S., Ghannam, S. F., Makhlouf, S., Green, A., Mongan, N. P., & Rakha, E. (2023). Expression, assessment and significance of Ki67 expression in breast cancer: an update. Journal of Clinical Pathology, 76(6), Article 357-364.

Journal Article Type Review
Acceptance Date Feb 6, 2023
Online Publication Date Feb 22, 2023
Publication Date Jan 18, 2023
Deposit Date Feb 21, 2023
Publicly Available Date Feb 23, 2023
Journal Journal of Clinical Pathology
Print ISSN 0021-9746
Electronic ISSN 1472-4146
Publisher BMJ
Peer Reviewed Peer Reviewed
Volume 76
Issue 6
Article Number 357-364
Keywords Ki67; Breast cancer; Assessment; Endocrine therapy; General Medicine; Pathology and Forensic Medicine
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