Potential immmunohistochemical markers to characterize epithelial-mesenchymal transition in pleomorphic adenoma.

Backgound: The histogenesis process of pleomorphic adenoma (PA) of salivary gland continues to remain a controversial subject. In this neoplasm, transition occurs from an epithelial or myoepithelial cell to a stromal element and is called an epithelial-mesenchymal transition (EMT) resulting in heterogeneity. The present research was aimed to study the morphological characteristics of varied components and epithelial-mesenchymal transitions in PA using histopathological and immunohistochemical (IHC) analysis.

Materials & methods: For this purpose 15 PAs cases were selected from the archives and from each case of PA and 5 cases of normal salivary gland, five additional sections were cut from each for immunohistochemical analysis using E- cadherin, vimentin and a-actin. The numbers of immunoreactive cells were semi- quantitatively measured and also determined the intensity of the immunostaining reaction.

Result: Immunohistochemically, as the cells transitioned from the lumial cells to descrete/detached cells of ductal structures, the percentage of positive cells tends to decrease for E- cadherin and increases for vimentin and actin. Additionally, neoplastic cells towards the periphery of ducal-cystic structures or completely detached cells in the stroma showed intense to moderate positivity for vimentin and alpha smooth muscle actin (a-SMA). Chondroid/ hyalinized or myxoid stroma showed variable staining with these markers.

Conclusion: Our study provides the evidence that epithelial-mesenchymal transition process represent the basic principle of the tisuse heterogeneity in pleomorphic adenomas.