Breast cancers in AA women are characterized by earlier onset, higher aggressiveness, more extensive metastases, and increased mortality rates compared to those in Caucasian women. A bewildering mystery confronting clinicians and cancer cell biologists alike is why some non-invasive breast cancers transform into aggressive tumors that readily metastasize to distant sites in the body. A simple and reliable test to predict metastatic risk in early-stage tumors has so far remained elusive. Clearly, the critical barrier to progress is a lack of knowledge of quantifiable properties of non-invasive lesions that predict the probability of faster kinetic progression to metastatic disease. Our goal is to address this vital knowledge gap by identifying cell biological characteristics underlying the disease's aggressiveness, thereby reducing the breast cancer-related health disparity between African American (AA) and Caucasian women. Our central hypothesis states that amplified centrosomes enhance cell polarization by organizing a compacted Golgi network that propels directed cell migration and invasion to accelerate metastases. The tantalizing possibility that organellar-level disparities may exist between tumors of differing metastatic potential has never been explored. Our novel paradigm that CA promotes metastasis is a groundbreaking conceptual advancement, which holds translational promise in early risk prediction. Our project will enhance understanding of 1) cell-biological traits of non-invasive lesions that determine metastatic risk, and 2) mechanisms by which cells acquire migratory and invasive capabilities that underlie metastases. The impact of our study will be on the development of 1) rapid, non-invasive centrosome-based detection methods (e.g. fine-needle aspirate cytology) which will allow early distinction between clinically-indolent and potentially fatal breast cancers, thus saving patients with indolent disease from unnecessary mastectomy, b) a method for early stratification of patients into subgroups with distinct centrosomal profiles, for effective risk-adapted treatment of breast cancer, c) a framework for improving success rate of clinical trials involving investigational drugs by establishing new criteria for patient classification. AIM 1 will establish differences in the incidence and severity of centrosome amplification between receptor- and grade-matched breast tumors from African American and Caucasian women. AIM 2 will determine molecular mechanisms that link amplified centrosomes to more aggressive tumor phenotypes. AIM 3 will pre-clinically develop small-molecule centrosome-targeted therapies for aggressive breast cancers, which will particularly benefit AA women, and reduce ethnic disparity in disease outcomes.