Abstract: Objective To investigate the relationship of tumor-associated CD34 fibroblasts and α-smooth muscle actin（α-SMA）in the nasopharyngeal carcinoma interstitium with invasion and metastasis by nasopharyngeal carcinoma. Method Expression of CD34 and α-SMA was measured by immunohistochemistry in 75 patients with nasopharyngeal carcinoma and 20 patients with chronic inflammation of the nasopharyngeal mucosa.Expression levels were compared with clinicopathological features of nasopharyngeal carcinoma using the supervised two-step method. Result Of the 75 cancer patients，7（9.33%） showed CD34 expression only in blood vessels and not in fibroblasts.In contrast，17 of 20 control patients（85.00%） showed CD34 expression not only in fibroblasts but also in small blood vessels of chronically inflamed tissue.These expression differences between the two groups were significant （χ²=31.542，P<0.01）.The proportion of patients expressing α-SMA was significantly higher in the nasopharyngeal carcinoma group（61/75， 81.33%） than in the control group（2/20，10.00%； χ²=51.263，P<0.01）. Correlation analysis of α-SMA expression with clinical and pathological features of nasopharyngeal carcinoma patients showed that the protein level was not related to age or gender （P>0.05）， but it was associated with clinical stage，T stage，lymphatic metastasis and distant metastasis（P<0.05）. Conclusion Fibroblasts in the nasopharyngeal carcinoma interstitium show phenotypic differences from the fibroblasts of chronically inflamed nasopharyngeal mucosa.These changes include lack of CD34 expression and overexpression of α-SMA.Expression levels of α-SMA appear to be related to nasopharyngeal carcinoma metastasis.

Key words: Nasopharyngeal neoplasm, Tumor-associated fibroblasts, α-SMA, CD34, Immunohistochemistry