Mast Cell Distribution in Oral Lichen Planus

Objectives: Oral lichen planus (OLP) is a common, intractable inflammatory lesion with chronic hyperkeratosis in the oral mucosa that is characterized by interlacing white lines, redness or erosion. Most zonal inflammatory cells in the subepithelial connective tissues of OLP comprise infiltrative lymphocytes, suggesting cellular immunity. On the other hand, mast cells that are preferentially distributed around the microvascular endothelium of the oral mucosa are essential in facilitating allergic reactions.The present study histopathologically examined the expression of mast cells in oral lichen planus. Methods: Samples from 18 patients who were pathologically diagnosed as lichen planus were stained with toluidine blue,distribution of mast cell was observed and then mast cells were counted from three locations under 400× magnification and the averages were calculated. We examined the relationship between the sites of occurrence and the type of this condition, and the presence of mast cells. Results: The average number of mast cells in the 18 samples was 13.1. The locations were as follows: buccal mucosa, 11; gingiva, 4; labial mucosa, 1 and buccal mucosa and gingiva, 2. The clinical types were classified to reticular, plaque, erosion and reticular, and erosion and plaque in 9, 2, 4 and 3, respectively. There was no relationship between must cell number and sites of lesion, nor clinical types. However, the mast cells were distributed in the underlying infiltrative lymphocytic or adipose tissue layers, which is typical of lichen planus. Conclusion: The distinctive distribution of mast cells suggested that they are involved in the pathogenesis of oral lichen planus.