Preoperative Testing of the Anti-Progesterone Mifepristone in Early Stage Breast Cancer

The primary objective of this study is to identify the group of women with early stage breast cancer most likely to benefit from treatment with the selective progesterone receptor modulator (SPRM) mifepristone. This will be done by treating women briefly prior to planned surgery and examining the decrease in growth rate (measured by Ki-67 immunohistochemistry) in tumor samples taken before and after exposure to mifepristone.