Immunohistochemical study of α-smooth muscle actin expression in oral leukoplakia and oral squamous cell carcinoma

CONTEXT: It is important to evaluate the role of stromal myofibroblasts (MFs) in carcinogenesis and also as a predictive marker for lymph node (LN) metastasis at the invasive front of oral squamous cell carcinoma (OSCC). AIMS: To demonstrate the expression of α-smooth muscle actin (α-SMA) by MFs in the tissues of oral leukoplakia (OL) with dysplasia and OSCC. To record and compare the distribution of MFs in OSCC with LN metastasis and without LN metastasis. SETTINGS AND DESIGN: Fifty paraffin-embedded tissue blocks with 10 cases of normal oral mucosa, 10 cases of OL with dysplasia and 30 diagnosed cases of OSCCs were studied. SUBJECTS AND METHODS: The samples were subjected to heat-induced antigen retrieval method followed by staining using primary mouse monoclonal antibodies against α-SMA and visualized using super sensitive polymer–HRP detection system. STATISTICAL ANALYSIS: Descriptive statistical analysis and ANOVA test were used for statistical analysis. RESULTS: There was no α-SMA expression in normal oral mucosa or in OL with dysplasia. All tissues of OSCC were positive for α-SMA expression. The difference in the expression between OL with dysplasia and OSCC was statistically significant (P < 0.05). The mean α-SMA count of OSCC with LN metastasis is significantly greater than in the OSCC without LN metastasis (P = 0.001). In OSCC without LN metastasis, focal and spindle patterns were predominant and in OSCC with LN metastasis network pattern was more. CONCLUSION: α-SMA expression by MFs in OSCCs indicates its role in tumor growth and invasion. The mean α-SMA count was found to correlate with tumor invasiveness and locoregional LN metastasis.