Our objective is to develop a novel optical assay system for intra operative assessment of tumor margins in partial mastectomy or mastectomy specimens. Our group has previously shown that optical techniques can effectively discriminate between malignant and non-malignant breast tissues. We have also shown that data collection and processing from a single point on the tissue specimen requires less than 5 seconds. In addition, the technique is easily adaptable to provide sensing depths that are required for breast margin assessment. The goal of the work proposed in this protocol is to test the sensitivity and specificity of an optical assay system developed by our group, for intra operative assessment of breast tumor margins.