This is a cohort study of women with suspected or confirmed recurrent breast cancer, with accessible tumor by standard clinical biopsy, prior to starting a new therapy for recurrent metastatic disease. Study participants will be ascertained from the population of all persons greater than eighteen years of age receiving care at the clinical practices of the Rowan Breast Center (RBC) at the University of Pennsylvania. The overarching goal of this study is to identify the genetic and molecular markers of molecular evolution identified in patients who have progressed from a primary diagnosis of breast cancer to recurrent, metastatic disease. As an observational study, this study seeks to gather data regarding the molecular and genetic changes that a primary cancer undergoes as a patient's cancer recurs and ultimately progresses. We anticipate enrolling 600 women with recurrent breast cancer who meet eligibility requirements for this study. Participation in this study will include the following: a biopsy and blood collection, completion of the study questionnaire, an optional bone marrow aspiration, and repeat collection of blood, offer of a research biopsy and a optional bone marrow aspirate collection at each progression time point. The study participants' medical information will be updated and changes in disease status will be captured on a regular basis.