Role of Mast Cells in Oral Lichen Planus and Oral Lichenoid Reactions

Oral lichen planus (OLP) is a chronic T cell mediated disease of oral mucosa, skin, and its appendages with a prevalence of 0.5 to 2.6% worldwide. Oral lichenoid reactions (OLR) are a group of lesions with diverse aetiologies but have clinical and histological features similar to OLP, thereby posing a great challenge in differentiating both lesions. Mast cells are multifunctional immune cells that play a major role in the pathogenesis of lichen planus by release of certain chemical mediators. Increased mast cell densities with significant percentage of degranulation have been observed as a consistent finding in pathogenesis of oral lichen planus.

The current study was aimed at quantifying the mast cells in histopathological sections of OLP and OLR thereby aiding a means of distinguishing these lesions.

The study group involved 21 cases of oral lichen planus, 21 cases of oral lichenoid reactions, and 10 control specimens of normal buccal mucosa. All the cases were stained with Toluidine Blue and routine haematoxylin and eosin and the mast cells were quantified.

The results were analyzed using the Kruskal-Wallis test and an intergroup analysis was performed using Mann-Whitney U test.

The number of mast cells showed an increased value in oral lichen planus when compared to oral lichenoid reaction and thus an estimation of mast cells count could aid in distinguishing OLP from OLR histopathologically.