MMP-13 expression in keratocyst odontogenic tumour associated with NBCCS and sporadic keratocysts. 
To investigate the matrix metalloproteinase (MMP)-13 expression in associated and non-nevoid basal cell carcinoma syndrome (NBCCS) Odontogenic Keratocysts (OCKs) in order to contribute to a better understanding of the differences in the growth pattern between them.  Thirty-nine paraffin-embedded blocks of OCKs, 26 sporadic OCKs and 11 NBCCS-associated KCOTs were studied by immunohistochemistry to evaluate MMP-13 expression both in epithelial and stromal layers.  A semi-quantitative scale was used to evaluate immunostaining.  Obtained data were compared between the two groups, using Fischer's exact test and the chi-square test.  Only 13 of 26 sporadic OCKs showed a positive immunostaining, whilst 11 KCOTs resulted in positive labelling for MMP-13 expression.  Moreover, syndromic cysts displayed a more intense and diffuse MMP-13 labelling of the stromal tissue.  Instead, in non-syndromic forms, the staining pattern of MMP-13 in stromal tissue was completely absent.  Fisher's exact test showed a statistically significant greater prevalence of KCOTs-immunolabelled cysts with respect to sporadic OCKs.  Results from this study point out that the biological behaviour of these cysts could be related not only to the epithelial layer but also to stromal tissue in that... MMP-13 overexpression in stromal tissue of NBCCS-associated KCOTs could clarify the higher aggressiveness of these cysts.