Evaluation of the Immunohistochemical Expression of iNOS in Oral Lichen Planus

Background: Oral lichen planus (OLP) is a chronic inflammatory disease with an unknown etiology. Because the evolution of OLP was influenced by a wide range of external and internal stimuli, it was crucial to study the expression of inducible nitric oxide synthase (iNOS) in OLP because of the known role of a wide variety of exogenous agents in exacerbating OLP’s onset. Objectives: To evaluate the immunohistochemical expression of iNOS and study its association with clinicopathological findings in OLP patients. Materials and Methods: This study was a retrospective analysis of 40 formalin-fixed paraffin-embedded tissue blocks of OLP that were detected and categorized as either reticular or erosive. For immunohistochemistry staining, a monoclonal antibody iNOS was utilized. Semiquantitative techniques were used to analyze the patterns of positively stained cells. Results: Forty biopsies from 24 female and 16 male OLP patients were included. The mean age was 49.15 ± 11.39 years. Using an immunohistochemical method, the results of the iNOS marker in this study showed that 18 (45%) cases had no staining, whereas 22 (55%) cases were positive. Regarding the density of iNOS marker expression, 50% of the cases had a score of 0, and 50% of the cases were positive, with a median final score index of 2, ranging between 0 and 5. Conclusions: Inducible nitric oxide is expressed in about 55% of OLP samples, which may, in turn, provide insight into the OLP’s pathogenesis.