# Ki-67 in triple-negative breast cancer

Source: https://onco.cc/terms/ki-67-in-tnbc/  
OnCo record `ki-67-in-tnbc` (Term). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

Ki-67 is a stain that marks dividing cells. Triple-negative cancers almost all score high, typically around 60 percent, so the marker separates them from slower hormone-driven cancers but rarely changes treatment within the triple-negative group; the international working group limits its clinical use to hormone receptor-positive disease.

## Summary

Ki-67 immunohistochemistry is a proliferation marker whose clinical use has been limited by questionable analytical validity. The International Ki67 in Breast Cancer Working Group (2019 meeting, published 2021) concluded that preanalytical handling is critical, recommended a standardised visual scoring method and quality assurance, accepted clinical validity as a prognostic marker, but found clinical utility only for prognosis in anatomically favourable ER-positive, HER2-negative T1 to T2, N0 to N1 disease, where 5 percent or less or 30 percent or more can be used to identify who does not need adjuvant chemotherapy (Nielsen 2021). Triple-negative tumours sit far above those thresholds: the Swedish population cohort of 5,655 tumours treated as triple-negative had a median Ki-67 of 63 percent in ER-zero and 60 percent in ER-low tumours (Acs 2024). Within triple-negative disease Ki-67 still carries information: in 105 Korean patients treated with neoadjuvant docetaxel and doxorubicin, tumours with Ki-67 of 10 percent or more had a pathological complete response rate of 18.2 percent against 0 percent below 10 percent, yet high Ki-67 was independently associated with worse relapse-free survival (hazard ratio 7.82) and overall survival, and the low-Ki-67 group showed a constant rather than early-peaking hazard of relapse (Keam 2011), the pattern of the luminal androgen receptor and special-type tumours. Grade 3 and high Ki-67 also enter the AJCC prognostic stage through grade. The ki-67-index readout and the ki67-mib1 assay records carry the scoring detail.

## Fields

- Kind: Term
- Last checked: 2026-09-24
- Also known as: Ki67 in TNBC; Proliferation index in triple-negative breast cancer; MIB-1 in triple-negative breast cancer
- Tags: breast; tnbc

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/Ki-67_(protein)
- Nielsen, JNCI 2021: International Ki67 in Breast Cancer Working Group updated recommendations: https://doi.org/10.1093/jnci/djaa201
- Acs, Lancet Reg Health Eur 2024: ER-zero and ER-low HER2-negative breast cancer treated as triple-negative, Swedish cohort: https://doi.org/10.1016/j.lanepe.2024.100886
- Keam, Breast Cancer Res 2011: Ki-67 classifies triple-negative breast cancer into two groups with different response and prognosis: https://doi.org/10.1186/bcr2834

## Connected records

- cancers: [HR-positive / HER2-negative breast cancer](https://onco.cc/cancers/breast-hr-positive/), [Luminal androgen receptor triple-negative breast cancer (LAR)](https://onco.cc/cancers/tnbc-luminal-androgen-receptor/), [Triple-negative breast cancer (TNBC)](https://onco.cc/cancers/tnbc/)
- technologies: [Histopathology & immunohistochemistry](https://onco.cc/technologies/histopathology-ihc/)
- terms: [AJCC 8th edition prognostic stage for breast cancer](https://onco.cc/terms/ajcc-prognostic-stage-breast/), [Grade](https://onco.cc/terms/tumour-grade/), [Pathologic complete response (pCR)](https://onco.cc/terms/pcr/)

---
JSON: https://onco.cc/api/v1/entities/ki-67-in-tnbc.json