Comparative immunolocalization of MMP-2, MMP-9 (magnification: 400×) and ColIV (magnification: 200×) in normal group, dysplastic oral mucosa group and OTSCC (T and S indicate the tumour and stroma respectively). (A, B) The expression of MMP-2 and MMP-9 in normal tongue mucosa epithelium are negative. (C) Continuous expression of ColIV in the BM adjacent to basal cells. (D) In dysplastic oral mucosa group, the expression of MMP-2 in the basal cell layer is increased. (E) MMP-9 expression is mainly located in the basal cell layer of dysplastic oral mucosa. (F) Fragmented expression of ColIV in the BM of dysplastic oral mucosa (black arrow). (G) In the OTSCC tissues, MMP-2 expression are mainly located in the stromal cells surrounding the nests of carcinoma. (J). In well-differentiated nests of carcinomas, the expression of MMP-2 was negative or weak positive. (H) The diffuse expression of MMP-9 are mainly showed in tumour and stromal cells. (K) MMP-9 positive cells were also accumulated around the blood vessels. (I, L) In the OTSCC, the expression of ColIV are showed fragmented or collapsed (I) and thick (L).