Correlation of growth fraction by Ki-67 immunohistochemistry with histologic factors and hormone receptors in operable breast carcinoma

Summary Breast cancer tissue samples obtained from 147 Stage I and II patients were tested with the monoclonal antibody Ki-67 and avidin-biotin-peroxidase complex in frozen sections. The percentage of cells with nuclear staining ranged from 5% to 65%. The frequency of Ki-67 positivity was classified in five groups: 0% (45/147 = 31%); 5–9% (38/147 = 26%); 10–19% (15/147 = 10%); 20–39% (24/147 = 16%) and 40% (25/147 = 17%). The mean value was 20%, median 18% with standard deviation of 14.5%. A significant positive correlation was observed between the presence of high Ki-67 nuclear staining rate with pathological tumor size (p = 0.003), histologic grading (p = 0.04), and axillary lymph node metastases (p = 0.009). An inverse significant correlation was found between Ki-67 and estrogen receptor expression (p < 0.001). No correlation was observed with progesterone receptor expression or menopausal status. The overall picture is of an inverse relationship between high growth fraction determined with Ki-67 antibody and tumor differentiation parameters. These correlations confirm those already reported by thymidine labeling index and flow cytometry methods.The proliferative rate determined with Ki-67 antibody may provide information regarding cell kinetics of breast carcinoma, potentially useful in identifying patients with a different clinical course in order to improve the therapeutic approach, by a rapid, practical and easily performed immunohistochemical method.