Statement of the Problem: Oral lichen planus (OLP) is a chronic inflammatory disease with unknown etiopathogenesis. It was believed that T cells played the major role in developing the lesions. It has been recently suggested that B cells and plasma cells may play a role in OLP pathogenesis.
Purpose: OLP is considered as a T-cell mediated disease. It was believed that the presence of B-cells and plasma cells in the sub-epithelial inflammatory infiltrate, rules out the diagnosis of OLP. This study aims to investigate the presence of B lymphocyte and plasma cells in the inflammatory infiltrate of OLP. Also the association between the presence of B cells and plasma cells with histopathologic features of the lesion was assessed.
Materials and Method: To assess the presence of B cells and plasma cells, 61 cases with the diagnosis of OLP were collected. The cases with definite clinical and histopathological diagnosis of lichen planus based on WHO criteria were included. For each case demographic information and histological characteristics were recorded. Specimens underwent immunohistochemical (IHC) staining for CD20 and CD138 and the percentage of the positive cells were counted and scored.
Results: CD20 positive cells existed in all OLP cases with the mean expression of 22.5% ± 15.17% and small number of CD138 positive cells were seen in 62.3% of our cases with the mean expression of 4.74% ± 9.23%. No association was found between histolopathological features and CD138 expression, however, CD20 expression level was higher in the cases with parakeratinized surface (p= 0.004).
Conclusion: B cells existed in the inflammatory infiltrate of OLP in all cases. Small number of plasma cells could be occasionally found in OLP. Therefore, presence of B cells and plasma cells in the inflammatory infiltrate cannot rule out the diagnosis of OLP.