The purpose of this study is to create a large-scale, population-based database that will match health information with genome (DNA) data to potentially identify new gene associations in breast cancer. The study focuses on patients who are being treated for stage I, II, or III breast cancer. Participants will not undergo any additional examinations, blood tests or medical procedures for purposes of the study. As part of routine breast cancer treatment, the participant’s doctor will provide tissue from their tumor to Agendia Breast Cancer tests for evaluation. Agendia Breast Cancer tests include MammaPrint and BluePrint, which are tests that help doctors analyze and profile the patient’s breast cancer tumor. The participant’s full genome data will be used for research purposes only. MammaPrint is used to determine the patient’s risk for distant metastasis (spreading of cancer). BluePrint provides physicians with more information about the type of breast cancer and the cancer’s biology. Participants’ full genome data will allow the study of new gene associations and additional biomarkers (biological indicators) that may be found to be relevant to breast cancer diagnosis and therapy. MammaPrint is approved by the U.S. Food and Drug Administration (FDA) for use in stage I and stage II breast cancer but may be ordered as experimental by the physician if the patient’s cancer is stage III.