 The aim of the study is to select 20 breast cancer patients, with primary tumors expressing PR 50 or higher and 1.5 fold PRA as compared with PRB, for a neoadjuvant treatment with mifepristone MFP during 14 days in between biopsy core and surgery. There are no studies at the present time selecting breast cancer patients according to the prevailing PR isoform expressed. This is extremely important since antiprogestins might have no effect or even stimulate those over-expressing PRB. 