Ki‐67 expression in breast carcinoma

Abstract

BACKGROUND The number of mitoses and, thus, the proliferative capacity of a tumor is one of the most crucial variables for tumor grading. The Ki‐67 nuclear antigen may be considered as an alternative to mitotic counts in grading schemes and as a single parameter that can be used in fine‐needle aspirates and small biopsies. METHODS Immunohistochemistry using the anti‐Ki‐67 antibody MIB‐1 was performed on 434 breast carcinoma specimens from the International Breast Cancer Study Group (formerly Ludwig) Trial V. Three groups based on Ki‐67 percent were used to replace the mitotic counts component in the Nottingham grade (NHG) to produce the Nottingham/Ki‐67 grade (NKG) and to assess Ki‐67 as a single parameter. RESULTS In both the lymph node positive subgroup and the lymph node negative subgroup, the NKG and Ki‐67 group was correlated significantly with Bloom–Richardson grade (BRG), NHG, and Nottingham type. Tumor size in the lymph node negative cohort and estrogen receptor status, progesterone receptor status, and c‐erbB‐2 expression in the lymph node positive cohort also were correlated significantly with NKG. Ki‐67 percentage was correlated significantly with c‐erbB‐2 expression in the lymph node positive cohort only. NKG was similar to BRG and NHG when it was evaluated for prognostic significance. Patients with higher categoric Ki‐67 percentages had worse overall and disease free survival in all groups except for the untreated, lymph node negative group. CONCLUSIONS Ki‐67 detection represents a valuable tool and is a good objective substitute for mitotic counts when used in a grading system. When it is used alone, Ki‐67 detection provides valuable information, although it is necessary to combine this with other parameters in the study of core biopsies and fine‐needle aspirates. Cancer 2003;97:1321–31. © 2003 American Cancer Society. DOI 10.1002/cncr.11188