In this cohort study, women with breast cancer and an indication for endocrine therapy will be prospectively enrolled. At the 1st visit (before the start of endocrine therapy (tamoxifen or aromatase inhibitor)) and at the 2nd visit (at \~3 months after the start of treatment), demographical / clinical data and blood samples will be collected. We will evaluate the hemostatic biological profiles associated with the use of endocrine therapy by comparing hemostatic biomarkers before and during its use.
