Histopathological and Immunohistochemical Study of the Distinction between Oral Lichen Planus and Oral Lichenoid Lesions

Background: Oral potentially malignant disorders, which include oral lichen planus (OLP), are clinical presentations that carry a risk of development to cancer in the oral cavity. Oral lichenoid lesions (OLLs) are also termed interface/lichenoid mucositis. Malignant transformation of them remains controversial, but distinct clinical and histological criteria for how to differentiate OLP from OLLs have not been developed. Objectives: The purpose of this study was to elucidate findings that can allow histopathological differentiation of OLP and OLLs using histomorphological and immunohistochemical analyses. Materials and Methods: Analyses were performed in 10 cases diagnosed with OLP and 9 cases diagnosed with OLLs. Cytokeratin 19 (CK19), Ki-67 and CD3 were used as primary antibodies to detect basal cells, proliferative activity and T-cell distribution, respectively, and Perlecan and COX-2 to evaluate epithelial intracellular arrangements and interstitial distributions of proteoglycans and enzymes. Results: For CK19, positive cells were significantly found in OLLs at both the prominent area and site adjacent to the lesion comparison with those of OLP’s. The number of COX-2 positive cells was significantly higher in spinous and basal layers in OLLs of the prominent area. Additionally, OLLs showed mild to moderate expression for perlecan in the basal to spinous layers and in subepithelial tissue. Conclusion: Almost no basal cells were noted in the prominent area in OLP. COX-2 and perlecan were found in the basal to spinous layers in OLLs. Although there are restrictions, these suggested the possibility of helping to distinguish between OLP and OLLs.

Histopathological Examination and Literature Review of Orthokeratinized Odontogenic Cyst

Background: With transitions in the disease concept of orthokeratinized odontogenic cyst (OOC), the pathogenesis and etiology have not been sufficiently elucidated. Objectives: OOC cases were reclassified and observed to understand the clinico-histopathological characteristics. In addition, literature review of OOC was performed to better organize the pathology. Materials and methods: Subjects with jawbone cysts lined by keratinized stratified squamous epithelium from 2005 to 2018 were reclassified, and clinico-histopathological findings were analyzed. Previous reports of OOC/orthokeratinized-type odontogenic keratocyst (OKC) from 1980 to 2019 were organized. Results: Five cases of OOC were diagnosed, representing 2.1% of odontogenic developmental cysts (total, 239 cases). Mean age was 37.6 years, with a female predominance. The mandibular molar area was the frequent site, and all cysts were solitary. Sixty percent involved an impacted tooth. Mean maximum diameter of the cyst was 2.2 cm. Histopathologically, 4 cases were unilocular, and partial palisading of the basal layer and scattered epithelial islands were observed in 2 cases each and formation of daughter cysts was noted in 3 cases. Previous papers described that most were unilocular and related to impacted teeth. Mean age ranged between 20 and 40 years, and the mandibular molar region was dominant. Recurrence rates were low. Conclusion: OOC shows a different biological attitude to OKC and is closer to dentigerous cyst. Meanwhile, OOC shows a similar histology of epidermoid cysts accompanying the granular layer. We thus surmised that OCC represents an independent concept as an odontogenic developmental cyst.