Retrospective analysis of MMS sensitivity and specificity. The MMS technique is an information rich modality providing both morphological and functional parameters of the interrogated tissue that could be correlated to known tumor pathology. However, this extracted information will require development of sophisticated spectral analysis models which would be beyond the scope of the current study. Therefore, for the purpose of this study, standard statistical techniques will be used to determine the classification power of MMS for tumor margin detection. While this approach does not fully elucidate the underlying pathology responsible for the classification, these types of models have been shown to perform at or better than those based on a morphological approach. This approach has been previously employed to classify skin cancer with high diagnostic accuracy. 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. This type of retrospective study will provide a proof of concept that would warrant further development and prospective studies of the MMS approach.