Laminin and collagen IV in pleomorphic adenoma and carcinoma ex-pleomorphic adenoma: an immunohistochemical study.

Laminin and collagen have been studied in several tumor types and their immunomorphological expression correlated with tumor morphogenesis, local invasiveness, and metastatic behavior. In a series of 53 cases of pleomorphic adenomas (PA) and 16 cases of carcinomas ex-pleomorphic adenoma (Ca ex-PA), we investigated by immunohistochemistry the distribution pattern of laminin (lam) and collagen IV (col IV) at the basement membrane (BM) and the interstitial compartments, and their potential relationship with the metastatic behavior of Ca ex-PA. At the BM compartment, lam and col IV were expressed in 37 and 41 of all cases, respectively. In PA, there were lam and col IV around cell aggregates in 47.2% and 56.6% of the cases, respectively, and around isolated cells in 30.2% and 26.4%, respectively. In Ca ex-PA cases, both antigens were expressed in 56.3% and in 18.8% of the cases around cell aggregates and isolated cells, respectively. At the interstitial compartment, the fibro-hyaline matrix contained few lam in PA (19.2%) in contrast to Ca ex-PA (75%), including the benign areas of the neoplasms (90%), being the difference statistically significant (P < .001). In the Ca ex-PA group, a statistically significant difference was found on col IV deposits around tumor cell aggregates between metastasizing and nonmetastasizing neoplasms (P < .001). These findings support that laminin and collagen IV are involved in the process of malignant transformation of pleomorphic adenomas and their biological progression.