Ki67 immunohistochemistry: a valuable marker in prognostication but with a risk of misclassification: proliferation subgroups formed based on Ki67 immunoreactivity and standardized mitotic index

Histopathology. 2006 May;48(6):674-82. doi: 10.1111/j.1365-2559.2006.02402.x.

Abstract

Aims: Counting mitotic figures is considered to be a reliable prognosticator, but evaluation of Ki67 immunohistochemistry has become more popular in evaluating proliferation. Our previous studies suggested an occasional discrepancy between mitotic figures and Ki67 fraction. The aim of this study was to investigate this more closely and also to study the associations between bcl-2 and p53 expression and proliferation.

Methods and results: Two hundred and sixty-five infiltrating breast carcinomas were immunostained for Ki67, p53 and bcl-2. The standardized mitotic index (SMI) was determined. Four proliferation groups were based on Ki67 positivity fraction and SMI at optimal cut-off points. Cox's multivariate model was used to test the power of the prognosticators. SMI and nodal status were the most powerful individual prognosticators. Ki67 was an independent prognosticator if nodal status, tumour size, age and histological grade were included in the analysis but not if analysed with SMI. The group with low SMI and low Ki67 fraction had the best prognosis. Groups with high SMI had the poorest prognosis. The group with low SMI and high Ki67 fraction had a favourable prognosis. Bcl-2 negativity and p53 positivity correlated with proliferation.

Conclusions: We have found a 'wrong positive' Ki67 group with favourable prognosis. SMI cannot be replaced by Ki67 because of the danger of misclassification of some patients.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Biomarkers, Tumor / analysis*
  • Breast Neoplasms / classification
  • Breast Neoplasms / metabolism
  • Breast Neoplasms / pathology*
  • Cell Proliferation
  • Female
  • Humans
  • Immunohistochemistry / statistics & numerical data
  • Ki-67 Antigen / analysis*
  • Logistic Models
  • Middle Aged
  • Mitotic Index / standards
  • Mitotic Index / statistics & numerical data
  • Multivariate Analysis
  • Prognosis
  • Proportional Hazards Models
  • Proto-Oncogene Proteins c-bcl-2 / analysis
  • Reference Standards
  • Risk Factors
  • Survival Analysis
  • Tumor Suppressor Protein p53 / analysis

Substances

  • Biomarkers, Tumor
  • Ki-67 Antigen
  • Proto-Oncogene Proteins c-bcl-2
  • Tumor Suppressor Protein p53