Expression of stem cell marker CD44 in selected benign and malignant salivary gland tumors

Background: Salivary gland (SG) tumors are among the unique neoplasms exhibiting complex histological features. The histogenesis remains unclear, and several pathways have been proposed. CD44 is a hyaluronic acid receptor that plays an essential role as an adhesion molecule for extracellular matrix components. The aim of the study is to investigate the expression of CD44 in selected SG tumors and determine its contribution to different biological behaviors of the tumors. Materials and Methods: CD44 expression was examined in 31 tumors using immunohistochemistry. CD44 was expressed in neoplastic cells of all tumors. Results: In pleomorphic adenoma, expression was more prominent in areas with ductal differentiation compared to myxoid areas. In all tumors, the proportion of tumor cells with positive staining ranged from 30% to 100%, except in adenoid cystic carcinoma, which expressed 10%–30% positive cells in two of the three samples analyzed. In conclusion, CD44 is expressed in epithelial neoplastic cells of pleomorphic adenoma, myoepithelioma, mucoepidermoid carcinoma, and adenoid cystic carcinoma. The relatively weak CD44 expression in plasmacytoid cells and myxoid areas of pleomorphic adenoma may indicate a more mature phenotype. Conclusion: There was no differential staining of CD44 among selected tumors. Further studies with a larger sample size and proper documentation are required.