Histomorphometric Evaluation of Intraepithelial Papillary Capillaries in Oral Lichen Planus: A Histopathological Study

Background: Definitive diagnosis of oral lichen planus (OLP) is important for planning treatment. The problems and difficulties of diagnosing OLP based on histopathological features were showing interand intra-observer variability. In terms of pathological diagnosis on OLP, microvascular appearance was not highly valued. Comparative histomorphometric analysis of intraepithelial papillary capillary loops (IPCLs) of OLP was performed to investigate the potential for use as diagnostic criteria. Methods: Immunohistochemical and histopathological evaluations of microvascular morphology were performed in 42 cases diagnosed as OLP clinico-histopathologically. Average areas and capillary loop angles at the sites adjacent to the lesion and most prominent and erosive areas of OLP were measured using image analysis software under microscopic observation. Results: Area of IPCLs in sites adjacent to the lesion was larger than those in prominent areas of OLP (p < 0.001). Capillary loop angles were 26.6 ± 19.3*, 84.5 ± 17.8*, 30.2 ± 2.4* and 34.4 ± 19.3* for normal mucosa, sites adjacent to the lesion, prominent areas of OLP, and erosive areas, respectively. Significant differences were observed between the prominent areas and adjacent sites to the lesion (p < 0.001). Conclusions: Characteristic IPCL patterns were identified in the present study despite reticular/erosive type. This research thus suggested the utility of these patterns in pathological diagnostic criteria. Introduction Lichen planus is a chronic inflammatory disease in the skin and mucous membranes of unknown etiology. Oral lichen planus (OLP) was first described by Wilson in 1869 [1], and appears more peculiar (that is, more persistent and resistant to treatment) than cutaneous lichen planus [2]. In addition, OLP was included as an oral potentially malignant disorders (OPMDS), defined as clinical presentation carrying a risk of cancer development in the oral cavity in the new World Health Organization classification of head and neck tumors [3], but the frequency of malignant transformation is controversial [4]. Therefore, definitive diagnosis in OLP is very important to decide treatment planning [5]. The diagnosis of OLP is based on both clinical and histopathological features. OLP clinically shows six classical clinical presentations, as described in the literature [6]: Reticular, erosive, atrophic, plaque-like, papular and bullous. In contrast, results of biopsy should be described, particularly when white striae are ill defined, plaques are present, or regions appear in any other way unusual [7]. Even though clinical and histopathological unified criteria for OLP have been unified [8], the potential for disagreement between clinical and histopathological OrIgInal arTICle