The incidence of skin cancer is increasing rapidly in the US. In 1994, there were around 1 million cases of non-melanoma skin cancer per year; this number had grown to more than 4 million by 2011. Many of these tumors appear in areas of the body that are exposed to sunlight (face, hands, etc.), where cosmetic considerations require minimizing resection of normal tissue. More generally, however, successful skin surgery requires the complete removal of diseased tissue while minimizing removal of healthy tissues. While standard surgical approaches may remove more healthy tissue than necessary or fail to remove all cancerous tissue, Mohs Micrographic Surgery (MMS) can achieve the above requirements, offering improved outcomes, lower chances of disease recurrence, better cosmetic results and minimal removal of healthy tissue compared to standard surgical approaches. However, MMS is time-consuming, has low patent throughput, requires specialized clinical training and on-site laboratory facilities. Moreover, it has been recommended that MMS only be used on a small subset of skin cancers conforming to specific characteristics [35]. The lack of a cost-effective, easy-to-use alternative to MMS and standard surgical approaches represents a significant, unmet clinical need that has yet to be addressed. In this Phase I submission, we propose to develop a simple, inexpensive and rapid imaging technology to identify cancer in resected tissues during surgery. Such a technology would bring the advantages of MMS surgery to many non-melanoma skin cancer resections while mitigating or eliminating the disadvantages of MMS. Our proposed approach is to topically apply a proprietary, smart, protease binding near- infrared fluorescent (NIRF) probe ex vivo to excised skin tumor tissue. Because many forms of cancer rely on specific proteases (known as cathepsins B or L) in order to invade surrounding normal tissue, the probe is designed to fluoresce under near-infrared light when it encounters active enzyme. Because it activates quickly, results can inform clinical decision-making almost immediately. The proposed technology can have a significant public health impact. Adaptation of this procedure into patient care can happen very rapidly and has the potential to radically improve the treatment of non-melanoma skin cancers, reducing costs, improving outcomes, and reducing complications for many patients. Phase I work involves: Studies to measure the activation of topically-administered probe by active proteases in skin biopsies. We will work with a Mohs-trained dermatologist to obtain discarded tumor tissue samples. We will apply probe to them and image them. Correlation of probe activation with cancer cells and active cathepsins. Statistical analysis to determine the accuracy (sensitivity and specificity) of the test to determine if it is useful as an intraoperative clinical tool to assess skin cancer resections.