Expression of matrix metalloproteinases (MMPs-2, -7, -9, and -26) and tissue inhibitors of metalloproteinases (TIMPs-1 and -2) in pleomorphic adenomas and adenoid cystic carcinomas

Purpose: To compare the immunohistochemical expression of matrix metalloproteinases-2, -7, -9 and -26 and tissue inhibitors of metalloproteinases-1 and -2 in pleomorphic adenomas and adenoid cystic carcinomas of the minor salivary glands. Methods: Twenty cases of pleomorphic adenomas and 20 cases of adenoid cystic carcinomas were evaluated for the immunohistochemical expression of matrix metalloproteinases-2, -7, -9, and -26 and tissue inhibitors-1 and -2 in tumor parenchyma. Results: Most pleomorphic adenomas and adenoid cystic carcinomas showed high expression of matrix metalloproteinases and tissue inhibitors, predominantly located in the tumor cells. There was no statistically significant difference in the expression of the metalloproteinases-2 (p = 0.359), -7 (p = 0.081), and -26 (p = 0 553), as well as the tissue inhibitors-1 (p = 0.657), and -2 (p = 0.248) between the parenchyma of the studied tumors. Only matrix metalloproteinase-9 showed a significant difference in expression between the two tumors, with adenoid cystic carcinoma showing a more intense staining for this gelatinase (p = 0.041). Conclusions: The expression of the studied metalloproteinases suggests the involvement of these enzymes in the tissue remodeling process in pleomorphic adenomas and adenoid cystic carcinomas, but only MMP-9, significantly expressed in the adenoid cystic carcinomas, appears to be involved in the process of invasiveness and more aggressive behavior of these tumors. Additionally, results point that TIMPs-1 and -2 may have more complex functions besides metalloproteinase inhibition, which may be related to the pathogenesis and biological behavior of salivary gland tumors.