Stains & molecular markers
Ki67 / MIB1

Topic Completed: 1 March 2018

Minor changes: 18 September 2020

Copyright: 2002-2020,, Inc.

PubMed Search: (Ki67[title] OR MIBI[title]) stain

Monika Roychowdhury, M.D.
Page views in 2019: 18,024
Page views in 2020 to date: 12,203
Cite this page: Roychowdhury M. Ki67. website. Accessed September 20th, 2020.
Definition / general
  • Marker of cell proliferation first described in 1983 (Int J Cancer 1983;31:13)
  • Name derived from Kiel, Germany (city of origin) and the clone number in the 96 well plate (Wikipedia)
  • Labile, nonhistone nuclear protein expressed in G1, S, G2 and M phases of cell cycle, then rapidly catabolized at end of M phase and not detectable in G0 and early G1 cells (J Cell Physiol 2000;182:311)
  • MIB1 is the IgG1 antibody against Ki67 for formalin fixed, paraffin embedded tissue
Essential features
  • Marker of cell proliferation
  • Nuclear stain
  • Considered a prognostic factor of breast cancer
  • Included in Oncotype DX® (21 prospectively selected genes to predict risk of recurrence and chemotherapy benefit in node negative, ER+ women)
Prognostic factors
  • Used for prognosis of relative responsiveness, resistance to chemotherapy or endocrine therapy and biomarker of treatment efficacy (high percentage reflects worse prognosis)
  • High Ki67 predicts higher recurrence and progression in nonmuscle invasive bladder cancer than those with low Ki67 expression (Oncotarget 2017;8:100614)
  • Superficial noninvasive papillary urothelial neoplasms of bladder show higher grade and recurrence with high Ki67 expression(Rev Col Bras Cir 2012;39:394)
  • Chordoma: matrix poor phenotype and higher rate of metastasis associated with high Ki67 expression; also, increase in progression associated with higher Ki67 (Eur Spine J 2016;25:4016)
  • Prostate cancer: High Ki67 associated with higher Gleason grade and worse prognosis (Br J Cancer 2013;108:271, Urol Ann 2015;7:488)
Uses by pathologists
Microscopic (histologic) description
Microscopic (histologic) images

Contributed by
Monika Roychowdhury, M.D.

Invasive ductal carcinoma breast 20x

Invasive ductal carcinoma 20x (Ki67)

Contributed by
Dr. Kaveh Naemi

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Lymph node, Burkitt lymphoma

Case #238

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Skin, symplastic glomus tumor, toe

Case #237

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Small bowel, malignant GIST

Case #202
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Cervix, adenocarcinoma in situ, endocervix

Case #194

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Urethra, clear cell adenocarcinoma

AFIP images

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Lymph node, normal

Contributed by
Leica Microsystems

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Tonsil, normal

Images hosted on other servers:
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Breast, invasive carcinoma, basal-like subtype with high Ki67 index

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Breast cancer: luminal A type

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Kidney, malignant solitary fibrous tumor

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Uterus (left to right), mid proliferative endometrium, day 17 endometrium

Board review style question #1
54 year old woman recently received the diagnosis of invasive ductal carcinoma for a right breast mass. Which of the prognostic markers below, if positive, suggest(s) aggressive behavior of the tumor?

  1. ER
  2. Ki67
  3. PR
  4. p63
Board review answer #1
B. Ki67
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