Molecular Profiling of Stage II and III Breast Cancer in Latin American Women Receiving Standard-of-Care Treatment

Background: \- Researchers want to learn more about breast cancer in Latin American women. They also want to learn how and why women respond differently to standard treatment. Tissue and blood samples from women with breast cancer are needed to study this disease in order to find new ways to prevent, diagnose, and treat it. Objective: \- To learn more about the biology and genetics of breast cancer in Latin American women. Eligibility: \- Latin American women age 18 and older of all ethnic backgrounds who have clinical stage II or III breast cancer. They must still be active and able to self-care. Design: * Participants are only agreeing to have extra tissue or blood samples collected. They are also letting tissue left over from surgery be used for research. No procedures outside of standard care will be done. * Participants may have a medical history, physical exam, and blood tests. They may have a pregnancy test. They may have an ultrasound, mammogram, and other scans. They may have an intravenous needle placed in an arm vein. * Participants may have a core biopsy. For this, a needle is inserted into the breast. A piece of tissue is extracted. * Participants who have chemotherapy may have blood taken after treatment/before surgery. Tissue may also be collected. * Participants will complete a questionnaire. It will ask about their social and economic background. It will ask about their family history of cancer. It will also ask about access to diagnosis and treatment of breast cancer. * Participants may be followed for up to 5 years.