Associations and indications of Ki67 expression with clinicopathological parameters and molecular subtypes in invasive breast cancer: A population-based study.

Ki67 has potential prognostic and predictive values for breast cancer patients, and has become an important biomarker in routine clinical practice. The aims of the present study were to investigate the distribution of Ki67 expression and its correlation with other clinicopathological parameters in central China. In total, 1,259 patients with newly-diagnosed invasive breast cancer were included in the present study. The clinical information was obtained from the electronic medical records. The expression levels of Ki67, estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER2) were detected by immunohistochemical analysis. The associations between Ki67 scores and other prognostic factors were evaluated as continuous and categorical variables. The mean value of the Ki67 scores of all patients was 31%. In total, ~36% (456/1,259) of the patients demonstrated a low expression of Ki67. A statistically significant correlation was identified between the mean Ki67 scores and the lymph node status, tumor grade, ER, PR and HER2 status, and clinical stage or molecular subtypes (all P<0.001). When Ki67 was categorized into high (>14%) and low (≤14%) level groups, the χ2 test was used to verify these results. The Ki67 scores demonstrated no statistically significant differences between the HER2-positive (non-luminal) and three negative subtypes, with the exception of patients with a tumor size of >2 cm (P=0.02). In conclusion, the results revealed the presence of significant correlations between Ki67 and other clinicopathological parameters.