MMP13 and skin squamous cell carcinoma: In view of this and the finding of MMP-13 up-regulation in SCC tissues, we sought to explore serum MMP-13 as a diagnostic marker for cSCC, and our results show that serum MMP-13 has high sensitivity and specificity for the differentiation of invasive cSCC and cSCC in situ (Fig. 4 a), and prediction of cSCC lymph node metastasis (Fig. 4 b).