Additional Study Information: The main purpose of this study is to determine the safety and tolerability of Faslodex given directly into thebreast ducts of women with invasive breast cancer or Ductal Carcinoma In Situ (DCIS). This study is for women who have been diagnosed with invasive breast cancer or DCIS. DCIS is the presence of abnormal cells inside a milk duct in the breast, and your cancer or DCIS treatment includes removing the afflicted breast, also known as a mastectomy.