Prognostic significance of syndecan-1 expression in squamous cell carcinoma of the tonsil

Syndecan-1 (SDC1) is reported to modulate several key processes of tumorigenesis and to show variable expression in many cancers. The cause of these variations in expression is not known to date. In this study, we compared SDC1 status with clinicopathologic parameters to evaluate the prognostic implications of SDC1 status on squamous cell carcinoma (SCC) of the tonsil. In 56 cases of tonsillar SCC, we screened SDC1 expression using immunohistochemistry and analyzed the relationships between SDC1 expression and clinicopathological parameters. To identify the cause of the changes in SDC1 expression seen in tumors, we measured the gene dosage of SDC1 in tumor cells using fluorescent in situ hybridization. SDC1 expression was found in cancer cells in 36 cases (64.3 %) of tonsillar SCC. It was associated with lymph node metastasis (p = 0.010) and a positive surgical resection margin (p = 0.014). On the other hand, it was not significantly correlated with sex, age, smoking status, degree of differentiation, T stage, or distant metastasis. We could not find any copy-number variation of SDC1 in the cases showing increased SDC1 immunopositivity. In addition, strong SDC1 expression in the tumor cells predicted a shorter overall survival (p = 0.020, log-rank). We showed that SDC1 expression is associated with N stage and the status of resection margin involvement in SCC of the tonsil. With respect to survival, there were unfavorable outcomes in cases with SDC1 positivity. More studies are needed to better understand the role of SDC1 in the progression and invasiveness of tonsillar SCC.