MMP13 and cancer: MMP-13 is a potent collagenase, which is rarely expressed in normal tissue, but which is often up-regulated when a rapid turnover of the ECM is required, as during the local invasion and growth of a malignant tumour.[34,51] MMP-13 is expressed at high levels in SCCs of the head and neck.[52–54] In our study, the intratumoural staining for MMP-13 (Figure 4) was graded as weak in 33% of the samples (19/57) and as strong in 67% (38/57).