No increased Ki67 expression in ductal carcinoma in situ associated with invasive breast cancer.

Introduction Several studies indicate that ;50% of patients with positive biopsies for DCIS of the breast may develop invasive breast cancer within 1–24 years of diagnosis (1). The biological mechanisms involved in the progression of DCIS to invasive cancer are not fully understood. Although Ki67 labeling indices increased in invasive breast cancer (2, 3), there are limited data on this marker in DCIS. Recently, Imamura et al. (4) reported that Ki67-associated proliferative activity of intraductal components (indicated by MIB1, an antibody that recognizes Ki67) is a significant prognostic determinant of disease-free survival in invasive ductal breast carcinoma. Allred et al. (5) found a differential expression of growth factor receptor HER-2/neu in DCIS with invasive disease versus DCIS without. On the basis of the above data, we conducted a case-control study of Ki67 in DCIS, with or without invasive breast cancer, testing the hypothesis that DCIS associated with invasive cancer would have a higher Ki67 expression than would DCIS alone.