A Comparative, semi-quantitative Evaluation of Myofibroblasts Between Mucoepidermoid Carcinoma and Pleomorphic Adenoma Using α -Smooth Muscle Actin Marker

Myofibroblasts are the main stromal components that constitute the desmoplastic reaction of host cells to inductive stimuli exerted by tumor cells. The purpose of this study was to evaluate the score of myofibroblasts using α -smooth muscle actin marker (α–SMA) in mucoepidermoid carcinoma (MEC) in comparison with pleomorphic adenoma (PA)and study the amount presence of these cells in those tumors.

The study included 20 cases of mucoepidermoid carcinoma and 20 cases of pleomorphic adenoma, using paraffin-embedded blocks that are appropriate for immunohistochemistry staining. 5 cases of mucocele and 5 cases of oral squamous cell carcinoma served as the negative and positive control. The expression of α -smooth muscle actin marker was determined by the immunohistochemically stained section. Myofibroblasts presence was assessed by a semiquantitative scale based on the score of immunopositive staining(0,1+,2+and 3+). The data were analyzed statistically with SPSS (ver.24) statistical software and using Mann-Whitney, Chi-Square, and Spearman`s correlation tests.

There are no significant differences in the mean score of positive cells for mucoepidermoid carcinoma and pleomorphic adenoma with mean and standard deviation (2.45±0.89) and (2.10±0.91) (Pvalue=0.182). Also, there are no significant differences between low and high grades of mucoepidermoid carcinoma (Pvalue=0.4).

In conclusion, despite the presence of α-SMA-positive myofibroblast cells in the connective stroma, PA capsule septa, and the stroma of MEC cases with different grades of malignancy, no significant difference was detected in the frequency of myofibroblast cells between the two groups.