Potential role of mast cells and eosinophils in establishing the clinical severity of oral lichen planus.

Background: Oral lichen planus (OLP) can be broadly classified clinically as an erosive (e) and non-erosive (ne) form. Mast cells (MCs) are granules containing cells that play an important role in the etiopathogenesis of OLP and have bidirectional interaction with eosinophil. In the present study, MCs and eosinophil densities were studied to find out if they could aid in the clinical severity of eOLP and neOLP.

Methods: The study group included 20 cases of eOLP and 30 cases of neOLP. All the sections were stained with special stains, toluidine blue (TB) for MCs and Congo red (CR) for eosinophils. Histopathological analysis was done by using Nikon NIS Elements Version 5.30 software (Nikon, Tokyo, Japan) by applying 100×100 µm grids to standardize the field of evaluation. Three subepithelial zones were demarcated as follows: 1) zone I was up to a subepithelial depth of 100 µm from the basement membrane; 2) zone II was beneath zone I from 100 µm to 200 µm; and 3) zone III was beneath zone II from 200 µm to 300 µm. In each of these zones, five high power fields with high cellular density were chosen to count MCs and eosinophils.

Results: The results of the study showed a significant increase in the number of MCs (intact and degranulated) in zone II and III compared to zone I in both eOLP and neOLP. Eosinophil density was significantly higher in zone II of both eOLP and neOLP when compared to zone I and III. We also observed a significantly higher number of both MCs and eosinophils in eOLP compared to neOLP. This difference was most prominent between zone II of eOLP and neOLP. No significant difference between granulated and degranulated MCs was found between the three zones.

Conclusions: Increased MC and eosinophil densities, as well as their interactions in eOLP, suggest that they play a significant role in etiopathogenesis and in establishing the clinical severity of the disease.