A novel technique to diagnose non-melanoma skin cancer by thermal conductivity measurements: Correlations with cancer stromal factors

The skin surface temperature reflects the physiological state of the human body. Quantitative methods of identification of skin cancers based on accurate measurement of effective thermal conductivity (ETC) are among the promising diagnostic tools for differentiating non-invasive and invasive melanomas before surgical treatment. To validate these findings, in this report, the diagnostic methods for invasive and non-invasive extramammary Paget's disease (EMPD) and squamous cell carcinoma (SCC) were further tested by measuring the absolute value of skin surface temperature and the ETC of the skin. In addition, to investigate the stromal factors that might affect ETC, immunohistochemical staining for LL37, periostin (POSTN), MMP12, and MMP28 was performed. The invasive SCC and EMPD group showed a relatively higher skin surface temperature compared to the in situ SCC group. The non-invasive EMPD and SCC group showed significantly lower values of ETC at lesions, whereas the invasive EMPD group showed significantly higher ETC values at lesions compared to healthy skin. Immunohistochemical staining showed that the percentage of LL37-producing cells was significantly increased in invasive EMPD and SCC compared to that in non-invasive EMPD and SCC. Moreover, Spearman's rank correlation test showed a significant inverse correlation between the percentage of MMP12-positive cells and increased levels of ETC-expressing areas in EMPD and SCC (r = -.5997). The present study suggested that differences in ETC could be a novel high-accuracy diagnostic technique for non-melanoma skin cancer, especially for detecting dermal invasion of SCC and EMPD.