Specific Aim 1: We hypothesize that a proliferative marker Ki-67 is reduced in patients with preinvasive Ductal Carcinoma In Situ (DCIS) and very early breast cancer treated with anastrozole. To establish reduction in Ki-67 as a primary surrogate endpoint to breast cancer risk reduction in patients treated with anastrozole we will measure Ki-67 before and after treatment with anastrozole. Consistent with this, it has been demonstrated by Geisler et al that patients with advanced breast cancer show a decrease in Ki-67 on lumpectomy/mastectomy samples when anastrozole is administered for few weeks prior to definitive surgery. In addition, there is a trend for a more profound suppression in those achieving an objective response. Ki-67 will be measured by routine immunohistochemistry.