Objective: Reactive hyperplastic lesions are one of the most common lesions of the oral cavity. Mast cells can be found in various oral lesions. However, the exact role of mast cells in oral reactive lesions is not fully understood. The aim of this study was to compare the mast cells count in various oral reactive lesions and to evaluate the correlation between the mast cells number and the intensity of inflammation.

Material and Method: This cross-sectional study was performed on 80 samples of oral reactive lesions including irritation fibroma, pyogenic granuloma, peripheral giant cell granuloma and peripheral ossifying fibroma (20 for each). Eight samples of normal oral mucosa were selected as the control group. To determine the mast cells count and the intensity of inflammation, Toluidine blue and Hematoxylin & Eosin staining was performed respectively. The data was analyzed with SPSS (V.21), Kruskal-Wallis, Tukey and Spearman's correlation coefficient tests.

Results: In this study, a significant increase in mast cells count was found in oral reactive lesions compared to normal oral mucosa (p<0.001). Difference of mast cell count between irritation fibroma and the peripheral giant cell granuloma groups (p=0.023), peripheral ossifying fibroma and peripheral giant cell granuloma groups (p=0.001) was statistically significant. There was a significant correlation between mast cell count and the intensity of inflammation in the irritation fibroma and pyogenic granuloma groups.

Conclusion: The finding of this study showed that mast cells count in peripheral ossifying fibroma and irritation fibroma were significantly higher than normal oral mucosa, so mast cells may have some role in the induction of fibrosis in oral reactive lesions.