Breast cancer is one of the most prevalent types of cancer in the world, and while treatments have advanced, significant room for improvement remains. About 30-60% of breast conserving surgery cases in the U.S. must be re-excised to obtain clear margins. In order to reduce the need for subsequent surgeries, new developments need to better assess tumor margins intraoperatively. Ultimately, the goal of my research is to find mass spectrometry signals to support surgical decision making in real time. Using mastectomy breast tissue samples, I will section and run tumorous and normal tissues as well as the 2cm and 5cm margins around the tumor through mass spectrometers. I will be looking for metabolites involved in glycolysis, the pentose phosphate pathway, and the citric acid cycle as biomarkers for breast cancers with various receptor statuses. These include estrogen (ER), progesterone (PR), and HER2/neu receptors. I will be looking at the following breast cancer subtypes: hormone receptor (HR) positive, Her2/neu positive, and triple negative. Using these biomarkers, surgeons will be better equipped to achieve clear margins and reduce the number of re-excisions, while decreasing turnaround time.