Stromal and epithelial syndecan-1 expression in benign and malignant salivary gland tumors: which is more reflective of behavior?

INTRODUCTION: Salivary gland tumors are a diverse group of lesions, with various origins and extremely different behaviors, leading to a variety of outcomes for patients. Therefore, the need to discover novel markers with the ability to predict the behavior of benign and malignant salivary gland neoplasms is crucial. Syndecan-1 is a cell-surface protein with significant roles in various aspects of tumor function. Its expression in salivary gland neoplasms, especially their stromal component, has not been investigated. OBJECTIVES: We aimed to assess the immunopositivity of syndecan-1 in epithelial and stromal components of salivary gland neoplasms and to compare it between benign and malignant subtypes in addition to evaluating its correlation with clinicopathologic parameters. METHODS: 133 salivary gland tumors were immunohistochemically stained with syndecan-1 and the intensity and percentage of this protein was determined, compared between the tumors and correlated with clinicopathologic factors. RESULTS: Statistical analysis of lesions with a sufficient sample size showed significant differences in percentage and intensity between both epithelial and stromal components of all tumors (p<0.05). Pairwise-comparisons demonstrated significantly higher staining-percentage of epithelial cells (p=0.02) in Warthin's tumor compared to pleomorphic adenoma and adenoid cystic carcinoma. Similarly, significantly higher staining intensities and/or percentages was observed in mucoepidermoid carcinoma and adenoid cystic carcinoma compared to pleomorphic adenoma and Warthin's tumor (p<0.05). Of the clinicopathologic factors, there was only a significant negative correlation between stromal percentage of mucoepidermoid carcinoma and age and a significant difference between stromal intensity+percentage of adenoid cystic carcinoma and gender (p<0.05). CONCLUSIONS: According to our findings we postulate that stromal syndecan-1 correlates with the behavior of salivary gland tumors, with malignant neoplasms demonstrating a higher expression, indicating a role for syndecan-1 in invasion and metastasis.