Abstract for presentation at 13th International Congress on Oral Pathology and Medicine

Introduction: The applicaion of immunohistochemistry methods has been resulted in marked improvement of the microscopic diagnosis of neoplasms in combined with H&E staining. Although unique cellular antigen has not been found in salivary gland neoplasms,multiple less specific immunomarkers have been used and may be helpfull in elucidating the role of myoepithelial differentiation in those neoplasms. The aim of this study was to evaluate immunohistochemical myoepithelial markers (GFAP Actin, Vimentin and S100 ) in mucoepidermoid carcinoma and pleomorohic adenoma of salivary gland.
Materials and methods: Formalin-fixed and parafin embedded tissue sections of 25 pleomorphic adenoma and 25 mucoepidermoid carcinoma were immunohistochemically analyzed for the presence of actin, vimentin, GFAP and S100 protein. A standard biotin-streptavidin procedure after antigen retrieval was used. Immunoreactivity of myoepithelial cells and chondromyxoid areas in pleomorphic adenoma, mucus cells,epidermoid cells and intermediate cells in mucoepidermoid carcinoma were evaluated and immunoreactivity was scored on a scale of 0 to 4+ (Regezi method) with 0 as negative, 1+ as scattered staining, 2+ indicate 25% to 50% of positive tumor cells and 4+ indicate more than 50% positive cells. The datas were analyzed with chi-square test.
Results: In 25 pleomorphic adenoma all nonluminal cells and chondromyxoid areas were 4+ for GFAP and vimentin,0 to 3+ for muscle-specific actin (12:0,12:1+,1:3+) and 1+to 4+ for S100 protein (3:1+,3:2+,18:3+,1:4+). But all mucoepidermoid carcinomas regardless of their grades were negative for all mentioned markers (p<0.001) and there were no immunohistochemical difference in major and minor salivary glands neoplasms.
Conclusion: Expression of myoepithelial cell associated markers in pleomorphic adenoma confirmed role of myoepithelial cells in histogenesis of this tumor and lack or limited exprtssion of these antigens in mucoepidermoid carcinoma indicated the minimal myoepithelial differentiation in this tumor. Therefore evaluation of myoepithelial cell markers can be helpful in differential diagnosis of salivary gland neoplasms with myoepithelial cell differentiation.