Features of differential diagnosis of lichen planus and lichenoid reaction of the oral cavity: histopathological analysis

Lichen planus is a chronic autoimmune skin-mucosal disease that often affects the oral cavity and can affect the esophagus, the mucous membrane of the genitals, the skin and its appendages. Lichenoid reactions are considered as lesions clinically similar to lichen planus erythematosus, but differing in pathogenesis, etiology and, consequently, treatment approaches. The main provoking factors of lichenoid reactions are medicines and dental materials. The aim of the study was to identify histopathological differences between lichen planus erythematosus and lichenoid reactions of the oral cavity for a more accurate differential diagnosis of these conditions. Materials and methods. The study included 35 patients of both sexes, aged 35 to 70 years, who sought treatment between 2019 and 2024. All patients were clinically diagnosed with lichen planus of the oral mucosa (L43) or lichenoid reaction of the oral mucosa (L43.8 according to ICD-10). Among them were 10 patients with erosive and ulcerative form, 12 patients with hyperkeratotic form of Lichen planus, 8 patients with exudative-hyperemic form of Lichen planus and 5 patients with lichenoid reactions in the oral cavity. All patients underwent an incision biopsy of the affected areas of the oral mucosa, followed by histopathological analysis. Results. Despite the similarity of clinical and histopathological signs of lichen planus and lichenoid reactions, the study revealed signs that allow them to differentiate. The presence of Sivatt bodies, hydropic degeneration and banded lymphocytic infiltrate are key diagnostic signs of lichen planus. Conclusions. Histological analysis of biopsy material should be considered as the main research method for making a final diagnosis when detecting lesions of the oral mucosa.