The research team will develop an intraoperative handheld device for assessing surgical margins during Mohs surgery. The device technology is based on multimodal optical spectroscopy (MMS), combining three optical spectroscopy techniques into one device. The researchers will first acquire proof of concept MMS measurements within the Mohs surgery suite immediately after surgical excision and prior to histological processing. MMS measurements will be acquired directly on the patient from the NMSC excision site. The final outcome of this study will result in the sensitivity and specificity of MMS compared to histopathology during Mohs surgery. These results will allow for the estimation of the potential benefit of an intraoperative margin assessment technique.