Challenges in the assessment of epithelial dysplasia in oral lichen planus and oral lichenoid lesion: Inter and intra-observer variability of the WHO criteria and binary system.

Background: Assessment of oral epithelial dysplasia is the gold standard for investigating the risk of malignant progression. The World Health Organization (WHO) methods and the binary system have limitations. This study assess the inter- and intra-observer variability of the architectural and cytological criteria and the classification of the presence and degree of epithelial dysplasia in oral lichen planus (OLP) and oral lichenoid lesion (OLL), using both the 2017 WHO criteria and the binary system. Material and Methods: The sample consisted of 65 biopsies from lesions classified as OLP and OLL according to the American Academy of Oral and Maxillofacial Pathology (AAOMP) criteria. The histological slides were reevaluated by two oral pathologists. Results: The individual alterations with most inter-observer disagreement were atypical mitotic figures (43.1%), loss of cohesion between epithelial cells (38.5%) and drop shape rete ridges ridges (38.5%). Inter-observer agreement analysis did not show statistically significant agreement regarding the classification of epithelial dysplasia grade by WHO criteria, only regarding the binary system classification (k=0.257; p=0.035). Intra-observer agreement analysis by evaluator 1 showed that the classification of epithelial dysplasia grade according to both methods had statistically significant agreement (k=0.546; p=0.004, k=0.861; p<0.001). Considering evaluator 2, only the evaluation of the WHO system classification showed statistically significant agreement (k=0.593; p=0.010). Conclusions: The evaluation of epithelial dysplasia is subjective and focal changes and inflammatory infiltrate, characteristic of OLP and OLL, can increase the degree of disagreement among evaluators. The binary system presents better inter-observer agreement, while the WHO system presents better intra-observer agreement. Key words:Oral lichen planus, oral lichenoid lesion, oral lichenoid disease, dysplasia, inter-observer variation.

Dentinogenic ghost cell tumor with focal atypical features suggesting ghost cell odontogenic carcinoma: Report of a challenging diagnosis.

Dentinogenic ghost cell tumor (DGCT) represents a rare benign odontogenic neoplasm that can appear in a central or peripheral form and may rarely undergo malignant transformation to ghost cell odontogenic carcinoma (GCOC). We aim to report a case of a central DGCT with focal cytological malignant aspects. A 24-year-old woman exhibited a painful enlargement and dental mobility in the left posterior maxilla for about one year, which appeared as an expansive well-defined hypodense maxillary image with hyperdense foci invading ipsilateral maxillary sinus. Incisional biopsy showed a predominantly solid hyperchromatic basaloid epithelium presenting cellular pleomorphism and mitotic activity, admixed with abundant ghost cell aggregates and dentinoid material. The lesion was immunopositive for p53 and had 21% of Ki-67 proliferation index (PI). These microscopic features suggested initially a GCOC diagnosis. Partial left maxillectomy was performed without complications. The surgical specimen presented an exuberant variation of the epithelial parenchyma, including ameloblastomatous, fusiform, and cribriform areas, with numerous ghost cells and dentinoid material, lacking any signs of malignancy. The final diagnosis was DGCT. The patient is in a strict regular follow-up for over two years, and there are no signs of recurrence.