Changes in major angiogenic proteins have been seen following initiation of tamoxifen and aromatase inhibitor therapy in women with breast cancer. One source of these proteins is the circulating platelet pool. The investigators hypothesize that in addition to their anti-platelet properties, agents such as aspirin can be used as targeted anti-angiogenesis therapy. The investigators will determine the influence of aspirin on the release of angiogenic proteins from platelets in 35 patients with breast cancer.