Clinical Characteristics, Identification, and Treatment of Lichen Planus: A Case Report.

Women are primarily affected by lichen planus, a chronic autoimmune skin and mucosal disorder in their 40s to 60s. Medication, systemic disorders, and mental stress are some of the factors that can cause it, though the precise cause is still unknown. Middle-aged females are the main victims of the disease; children are rarely affected. Oral lichen planus (OLP) is less common in atrophic and erosive forms. There is disagreement over whether OLP causes cancer; therefore physicians need to keep a close watch for any intraoral lichenoid lesions, and patients with OLP are advised to follow up regularly. This case report details a 52-year-old woman's right buccal mucosa and tongue affected by reticular lichen planus.

Antitubercular drug-induced lichen planus: A case study with a mini literature review.

Introduction: Drug-induced lichen planus is a cutaneous adverse effect that manifests as a systemic eruption of flat-topped, erythematous, or violaceous papules resembling lichen planus on the trunk and extremities. Although antitubercular therapy has been linked to cutaneous hypersensitivity reactions, the literature on such cases is scarce. Here, we present a case to contribute to this field, reporting on its presentation and management, and reviewing previous case studies. Case Report: Our patient, a 63-year-old male, presented with black pigmented patches on the skin, having been diagnosed with pulmonary tuberculosis and on antitubercular therapy for the past two months. A diagnosis of ATT-induced lichen planus was made, and all ATT was stopped. The patient was treated with antihistamines, apremilast, tacrolimus, and corticosteroids, and rechallenge of each drug was performed consecutively. No new lesions appeared after rechallenge with isoniazid and rifampicin. However, ethambutol was not reintroduced due to strong suspicion, by exclusion, that it was the offending agent, whereas on rechallenge with isoniazid and rifampicin, the patient's skin lesions gradually improved with eventual resolution of hyperpigmentation. Discussion and Conclusion: Lichenoid drug eruptions are characterized by type IV hypersensitivity reactions, and rechallenge is required to ensure safer treatment since the risk of disseminated and multi-drug-resistant tuberculosis increases with the cessation of antitubercular therapy.

Camrelizumab-induced oral lichenoid reaction with subepithelial CD4+ T-cell infiltration.

INTRODUCTION: Camrelizumab is a novel anti-programed cell death-1 (PD-1) antibody that has been investigated for the treatment of various malignancies. Increasing immune-related adverse events have been reported in clinical practice, with CD4+ T-cell-mediated-reactive cutaneous capillary endothelial proliferation being the most common. Camrelizumab-induced oral lichenoid reaction (OLR) appears to be a rare adverse effect compared with other anti-PD therapies induced OLR, with the main pathogenesis of activated CD8+ T cells mediating autoimmune reactions. Herein, we report a rare case of camrelizumab-induced OLR and a possible pathogenic mechanism of subepithelial CD4+ T-cell infiltration. CASE REPORT: A 57-year-old male patient, who was diagnosed with metastatic esophageal squamous cell carcinoma three years prior, presented with a two-month history of oral erosion that developed while under camrelizumab therapy. Diffuse erythematous and erosive lesions surrounded by bilateral white lesions on the buccal mucosa were detected in his physical examination. Hematoxylin and eosin staining of the lesions revealed the presence of basal keratinocyte degeneration and band-like subepithelial T-cell infiltration. The immunostaining for CD4 on T-cell was positive, while CD8 were sporadically positive. Flow cytometry showed a gradual increase in the CD4+ T-cell proportion in the peripheral blood, with the CD8+ T-cell percentage almost unchanged and in the normal range. We obtained a score of 6 based on the Naranjo algorithm, which means a probable adverse drug reaction. MANAGEMENT AND OUTCOME: The patient exhibited notable improvement after two weeks of treatment with topical glucocorticoid without regulating his immunotherapy, and remained in stable condition in the follow-up. DISCUSSION: This case may offer new insight to clinicians on the pathogenesis of anti-PD-1-induced OLR. More critically, it may provide some ideas for a more precise anti-PD therapy or corresponding combination therapy for patients becoming resistant to immunotherapy due to exhausted CD4+ T-cell responses in the tumor microenvironment.

A Novel Approach to Differentiating Erosive and Reticular Lichen Planus Based on the Percentage of Dental Surfaces With Metal Restorations.

Introduction Oral lichen planus (OLP) and oral lichenoid reaction (OLR) constitute clinical entities with strong but unclear etiologic relation to dental materials. The aim of this study was to evaluate a correlation between the clinical form of OLP/OLR and the number of dental metal restorations in the oral cavity thus utilizing an exposure to metal (EM) index.  Material and methods The study type is experimental, and the study design is characterized as semiquantitative research that belongs to the branch of experimental research. Twenty-nine patients were chosen based on clinical (either reticular or erosive clinical forms) and histologic findings suggestive of OLP/OLR. The files of patients were retrieved from the archives of the Department of Oral Medicine/Pathology, School of Dentistry, Aristotle University of Thessaloniki, Greece, during the period 2009-2019. The medical history of the patients did not include any disorder or medication associated with lichenoid lesions and the measurements took place concurrently with the establishment of the diagnosis, thus no treatment for the lichen planus had been administered prior to the measurements. Quantitative measurement of the percentage of dental surfaces restored through metal restorations and correlation with the clinical and histologic findings of OLP/OLR was evaluated. The EM index was evaluated on a scale of 1-3, which corresponds to the percentage of dental surfaces restored through metal restorations. The statistical analysis was performed with the Pearson chi-square test and the significance level was set at p≤0.05. Results The EM index was measured by dividing each tooth into five surfaces (occlusal, mesial, distal, buccal, lingual), subsequently multiplying the number of available teeth with the number 5 to calculate the total number of surfaces, and then counting the number of surfaces with metal restorations - both fillings and crowns (in case of metal-ceramic crowns, the respective dental surface is taken into account only in case of macroscopically exposed metal), dividing the number of surfaces with metal restorations with the total number of surfaces and multiply by 100 so that the results take the form of percentages (%) and finally classifying the percentages into three groups: 1: 0% metal restorations, 2: 1-25% metal restorations, 3: >26% metal restorations). The percentage in female patients ranged from 0% to 100%, whereas it ranged from 0% to 60% in male patients. According to the clinical form of the lichenoid lesion, the percentage ranged from 0% to 60% in reticular lichen planus cases and from 0% to 100% in erosive lichen planus cases. There was no statistical difference between lichen planus cases, in total, and in normal oral epithelium. However, the levels of EM were marginally similar between the reticular lichen planus and the erosive lichen planus (Fisher's exact test, p = 0.056). Therefore, it may be the case that the EM index is higher in erosive lichenoid lesions. Conclusion In our study, the EM index was higher in female patients and in erosive lichenoid lesions. These findings should be tested and supported by larger samples of patients since the aforementioned Fisher's Exact Test, p = 0.056 could fall below the threshold of 0.05 if more patients were included. This is the first attempt to establish a novel approach to differentiating erosive and reticular lichen planus based on the percentage of dental surfaces with metal restorations.

Cancer Stem Cells' Biomarker ALDH1&2 Increased Expression in Erosive Oral Lichen Planus Compared to Oral Leukoplakia.

INTRODUCTION: ALDH1&2 has been considered an oral cancer stem cell (CSC) marker. Oral carcinogenesis is a process that usually passes through oral potentially malignant disorders (OPMD). Oral lichen planus (OLP) consists of immune-related chronic disorders that have been included in the OPMDs due to their possible transformation into oral cancer. The aim of this study was to investigate the early presence of ALDH1&2 in OLP compared to early oral leukoplakias (OL), especially mildly and non-dysplastic OL. MATERIALS AND METHODS: The study type is experimental, and the study design is characterized as semiquantitative research which belongs to the branch of experimental research. The study sample consisted of paraffin-embedded OLP biopsy samples from the archives of the Department of Oral Medicine/Pathology, School of Dentistry, Aristotle University of Thessaloniki, Greece, during the period 2009-2019. The study sample contained 24 cases of OLP (14 erosive and 10 reticular) and 30 cases of OL (16 cases of moderately and severely dysplastic OL and 14 cases of mildly and non-dysplastic OL). The CSC-related biomarker ALDH1&2 was examined using semiquantitative immunohistochemistry (monoclonal antibody sc-166362, Santa Cruz Biotechnology, Dallas, Texas, USA, 1:100). ALDH1&2 expression was evaluated through a scale of 1 to 3 depending on the percentage of positive epithelial cells and was compared to normal epithelium as well as cases of OL (the most prominent OPMD). The statistical analysis was performed with the Pearson chi-square test and the significance level was set at p≤0.05. RESULTS: The cytoplasmic staining of ALDH1&2 was observed mostly in the epithelial cells of the basal layer of the epithelium of OLP. Overall, this expression was significantly increased compared to normal epithelium. In addition, statistically significantly higher expression of ALDH1&2 was observed in the erosive form of OLP. Interestingly, this OLP positivity was higher compared to mild and non-dysplastic leukoplakias (p<0.001). CONCLUSIONS: ALDH1&2 is a confirmed CSC marker that was found to be clearly increased in OLP and characteristically in erosive OLP epithelium for the first time. Noteworthy, it was more prominent in erosive OLP rather than in mildly and non-dysplastic OL. Whether this pattern of expression raises the red flag of an early epithelial "CSC" phenotype in OLP or that ALDH1&2 expression indicates a response to the OLP inflammatory process requires further investigation.

Oral Manifestation in Postmenopausal Women of Maharashtra, Western Region.

Introduction: Menopause in women is a physiological state that gives rise to adaptive changes at both the systemic and oral levels. The oral manifestations of postmenopausal women may vary for each patient. It occurs in the form of burning mouth syndrome, xerostomia, periodontitis, etc., We aimed to assess the prevalence of oral manifestations in the postmenopausal population, to know the nature and severity of oral manifestations occurring in postmenopausal women, and to assess the systemic conditions of these postmenopausal women with oral manifestations. The study was designed to assess the oral manifestation in postmenopausal women of Maharashtra, Western region. Materials and Methods: The study was conducted in the department of oral medicine and radiology. A total of 90 patients were included. A detailed clinical examination was done using a mouth mirror and probe. The clinical pro forma recorded demographic data, including the duration of menopause and different oral manifestations like xerostomia, periodontitis, lichen planus, oral candidiasis, etc., Collected data were entered into MS Excel and subjected to statistical analysis. Results: In the study, there were a total of 90 patients. These patients were distributed into three groups based on their age groups. The majority of the oral manifestations were reported in patients belonging to Group 2 (60-70 years age group). Conclusion: Overall, 76.6% of patients reported oral mucosal changes; of which 20.2% of patients reported xerostomia, 15.9% reported periodontitis, 13% showed altered taste, 8.6% of patients had lichen planus, and 7.2% patients reported oral candidiasis and space infections.

Oral Potentially Malignant Disorders and Candida in Oral Tongue Squamous Cell Carcinoma Patients.

This retrospective study addressed the role of oral potentially malignant disorders and the presence of intraepithelial Candida hyphae in the carcinogenesis of the oral tongue squamous cell carcinoma and its association with smoking, alcohol consumption, and oral inflammatory burden. The medical records of 183 subjects diagnosed with oral tongue squamous cell carcinoma at the Helsinki University Hospital were investigated. Preceding oral lichen planus, lichenoid reaction, and leukoplakia diagnosis were recorded. Further, the data on Candida hyphae in histological samples as an indicator of oral candidiasis, oral inflammatory burden, smoking, and alcohol consumption were recorded and analyzed. The histopathological diagnosis of oral lichen planus/lichenoid reaction (p < 0.001) and the presence of Candida hyphae (p = 0.005) were associated significantly with female gender. Oral lichen planus/lichenoid reaction patients were less often smokers than patients without these lesions. Candida hyphae were more often recorded in patients without alcohol use (p = 0.012). Oral lichen planus/lichenoid reaction and Candida hyphae in histological samples were associated with female gender and lower levels of typical risk factors, such as alcohol use and smoking, in oral tongue squamous cell carcinoma patients. Therefore, these patients should be well monitored despite a potential lack of the classical risk factors of oral carcinoma.

Prevalence of and prognostic factors for Candida superinfection in oral lichen planus and lichenoid reactions: A retrospective cohort study.

BACKGROUND: Oral candidiasis occasionally occurs in patients with oral lichen planus (OLP) or lichenoid reaction (OLR). However, not all patients undergoing corticosteroid therapy develop Candida superinfection. Thus, the identification of prognostic risk factors may help to identify patients at risk of Candida superinfection. METHODS: A retrospective cohort study was conducted to review patients with OLP/OLR who received steroid therapy at a single dental hospital between January 2016 and December 2021. The prevalence of Candida superinfection and prognostic factors were assessed. RESULTS: Eighty-two eligible patients with OLP/OLR were retrospectively reviewed. The overall prevalence of Candida superinfection during the study period was 35.37%; the median time-to-event between initiation of corticosteroid therapy and diagnosis of superinfection was 60 days (interquartile range; 34-296). The ulcerative type of OLP/OLR, number of topical steroid applications, poor oral hygiene, and oral dryness were significantly associated with superinfection (p < 0.05; Fisher's Exact test) and were identified as prognostic factors in univariable risk ratio regression. Multivariable risk ratio regression revealed the ulcerative type of OLP/OLR and number of topical steroid applications were significant prognostic factors for Candida superinfection in patients with OLP/OLR. CONCLUSION: Candida superinfection occurs in approximately one-third of patients with OLP/OLR undergoing corticosteroid therapy. Patients with OLP/OLR should be closely monitored in the first 2 months (60 days; median time to infection) after steroid prescription. The ulcerative type of OLP/OLR and a higher number of topical steroid applications per day may represent prognostic factors to identify patients at risk of Candida superinfection.

COVID-19 Vaccine-Induced Lichenoid Eruptions-Clinical and Histopathologic Spectrum in a Case Series of Fifteen Patients with Review of the Literature.

Lichen planus is a distinctive mucocutaneous disease with well-established clinical and histopathologic criteria. Lichenoid eruptions closely resemble lichen planus and may sometimes be indistinguishable from it. Systemic agents previously associated have included medications, viral infections and vaccines. Sporadic case reports of lichen planus and lichenoid reactions associated with COVID-19 vaccines have recently emerged. Herein, we review the world literature (31 patients) and expand it with a case series of 15 patients who presented with vaccine-induced lichenoid eruption (V-ILE). The spectrum of clinical and histopathologic findings is discussed with emphasis on the subset whose lesions manifested in embryologic fusion lines termed lines of Blaschko. This rare Blaschkoid distribution appeared in seven of the 46 patients studied. Of interest, all seven were linked to the mRNA COVID-19 vaccines. We believe that all lichenoid eruptions should be approached with a heightened index of suspicion and patients should be specifically questioned with regards to their vaccination history. When diagnosed early in its course, V-ILE is easily treated and resolves quickly in almost all patients with or without hyperpigmentation. Additional investigative studies regarding its immunopathology and inflammatory signaling pathways may offer insight into other Th1-driven autoimmune phenomena related to COVID-19 vaccination.

Senescence in oral lichen planus as assessed by the immunohistochemical evaluation of senescence marker protein-30 (Regucalcin).

Background: Oral lichen planus is a T-cell-mediated chronic inflammatory disease affecting approximately 1% to 2% of the population, the etiology of which is currently unknown. The objectives of this study were to observe if senescence occurs in oral lichen planus, through the assessment of the immunohistochemical expression of a novel marker for senescence called Senescence marker protein-30 or regucalcin, and compare the expression to that in oral lichenoid reaction and non-specific inflammation. Subjects and Methods: The study material consisted of 30 cases of oral lichen planus, 15 cases of oral lichenoid reaction and 15 cases of non-specific inflammation. The number of positive cells in ten randomly selected high power fields were counted in the epithelium and the connective tissue separately and the mean was determined. Results: Mann-Whitney U test was used to statistically analyze if there was any significant difference in the expression of Senescence marker protein-30 between oral lichen planus, oral lichenoid reaction and non-specific inflammation. Even though a greater expression was seen in the oral lichen planus cases than oral lichenoid reaction, the difference in both the epithelium and connective tissue was not statistically significant. Conclusion: This study shows that in addition to the already known mechanisms like apoptosis and increased cell proliferation rates, the activated T-lymphocytes may also trigger a senescent change in the cells of oral lichen planus. As with the other mechanisms, this is also seen only in a small proportion of the cases.

Narrow-band imaging features of oral lichenoid conditions: A multicentre retrospective study.

OBJECTIVE: Narrow-band imaging (NBI), which highlights epithelial intrapapillary capillary loops (IPCLs) classified into five patterns (0 toIV) with increasing correlation to malignancy, has demonstrated effectiveness for detection of oral squamous cell carcinoma (OSCC). Lack of standardised procedures limits its use for routine inspection of oral lichenoid lesions including oral lichen planus (OLP), oral lichenoid lesion (OLL) and oral lichenoid reaction (OLR). The aim of this study was to analyse IPCL patterns of such lesions, assessing correlations with histopathological outcomes. MATERIALS AND METHODS: A multicentre, retrospective study was performed on 84 patients who underwent NBI and subsequent biopsy for suspected OLP/OLL/OLR. Patients were examined with Evis Exera III NBI system. Recorded NBI video endoscopies were evaluated to assess IPCL patterns and correlated with histopathological outcomes. RESULTS: No significant differences were detected among OLP/OLL/OLR on NBI inspection. All lichenoid lesions were significantly related to low-grade (0-II) IPCL patterns, clearly distinguishable from OSCC, showing pattern IV (p < 0.05). CONCLUSIONS: NBI cannot discern among OLP/OLL/OLR lesions. Interpretation should be modulated when assessing lichenoid lesions. NBI has potential to discern malignant transformation occurring in lichenoid lesions undergoing long-term follow-up, as IPCL pattern IV may be used as a clinical marker of malignancy arising in chronic inflammatory lesions.

Lymphocyte and CD62E expression in lichen planus and lichenoid reaction.

BACKGROUND: It is difficult to distinguish the clinical and histopathological aspects of oral lichen planus lesions from those of oral lichenoid reaction. Some criteria were proposed to distinguish them, mainly because they have different biological behaviors. The aim of the present study was to compare the lymphocyte population and the expression of E-selectin between these lesions. METHODS: Participants with a clinical diagnosis of oral lichen planus (GOLP) and oral lichenoid reaction (GOLR) who needed to perform a biopsy were selected. The tissue was frozen and immunostaining was performed for CD3/CD4, CD3/CD8, CD4/CLA, CD8/CLA, and CD62E. The analysis of each immunostaining was accomplished using the ImageJ program. RESULTS: In total, 25 participants with oral lichen planus and 11 with oral lichenoid reaction were seen. In the evaluation of CD3 + CD4+/CD3 + and CD3 + CD8+/CD3 + proportions, there was a higher percentage of these cells in the oral lichen planus group when compared with the oral lichenoid reaction group (p = 0.027 and p = 0.038 respectively). The average number of CLA + lymphocytes for CD4+/CLA + and CD8+/CLA + in both groups was not statistically significant (p = 0.840; d = 0.363). In GOLP, the number of CD4 + CLA+/E-selectin and CD8 + CLA+/E-selectin was not statistically significant (p = 0.951 and p = 0.454 respectively); neither in GOLR (p = 0.454 and p = 0.989 respectively). CONCLUSION: Our results indicate that CD3 + CD4+, CD3 + CD8+, CD4 + CLA+, CD8 + CLA + lymphocytes and E-selectin are present in both lesions. However, the proportion of CD3 + CD4+/CD3 + and CD3 + CD8/CD3 + cells is higher in the oral lichen planus group when compared with the oral lichenoid reaction group, suggesting that these cells may be important for the etiopathogenic mechanism of these lesions.

Gold Dental Implant-Induced Oral Lichen Planus.

Lichen planus is a chronic inflammatory cutaneous and mucosal disease mostly affecting middle-aged individuals. The etiology of lichen planus is unknown, but current literature suggests that it is an altered immune response characterized by dysregulated T-cell activation and subsequent inflammation which can be associated with conditions like allergic contact dermatitis and hepatitis C. Additionally, heavy metals like lead, tin, arsenic, and bismuth can create inflammatory and allergic reactions that can predispose to the formation of lichen planus. This report examines the case of a 64-year-old female with longstanding oral lichenoid lesions with superimposed Wickham's striae, allergic skin reactions to several medications, and a history of receiving gold-containing dental implants. As a result of her history and subsequent allergy testing, she was found to have a gold allergy. The constant mucosal irritation from her dental implants likely was associated with the development of her oral lesions, which were confirmed to be oral lichen planus. She was recommended to apply triamcinolone 0.1% ointment to her oral lesions and to follow up with her dentist for evaluation of her filings. Further, it was recommended she replaces the dental crowns with compounds lacking gold to decrease the persistent irritation. This case represents the first such instance of gold dental fillings directly having an appreciable role in the development of oral lichen planus.

Oral Immune-Related Adverse Events Caused by Immune Checkpoint Inhibitors: Salivary Gland Dysfunction and Mucosal Diseases.

Conventional chemotherapy and targeted therapies have limited efficacy against advanced head and neck squamous cell carcinoma (HNSCC). The immune checkpoint inhibitors (ICIs) such as antibodies against CTLA-4, PD-1, and PD-L1 interrupt the co-inhibitory pathway of T cells and enhance the ability of CD8+ T cells to destroy tumors. Even in advanced HNSCC patients with recurrent diseases and distant metastasis, ICI therapy shows efficiency and become an effective alternative to conventional chemotherapy. However, as this therapy releases the immune tolerance state, cytotoxic CD8+ T cells can also attack organs and tissues expressing self-antigens that cross-react with tumor antigens and induce immune-related adverse events (irAEs). When patients with HNSCC are treated with ICIs, autoimmune diseases occur in multiple organs including the skin, digestive tract, endocrine system, liver, and respiratory tract. Treatment of various malignancies, including HNSCC, with ICIs may result in the appearance of oral irAEs. In the oral cavity, an oral lichenoid reaction (OLR) and pemphigoid develop. Sicca syndrome also occurs in association with ICIs, affecting the salivary glands to induce xerostomia. It is necessary to elucidate the pathogenic mechanisms of these intractable diseases that are not seen with conventional therapy. Early diagnosis and appropriate approaches to irAEs are needed for efficient treatment of advanced HNSCC by ICIs.

Severe oral ulcerative and lichenoid lesions associated with adrenal insufficiency in a patient treated with nivolumab: Report of a case and review of literature.

Nivolumab, an antibody against anti-programmed death type 1, has been used for treatment of advanced non-small cell lung cancer with improvement of overall survival. Usually, diarrhea, cutaneous rash, and pruritus are reported as the most common immune-related adverse effects of nivolumab therapy. Oral lesions and secondary adrenal insufficiency sometimes occur but usually are rare events. We report a case of a patient treated with nivolumab who then showed persistent oral ulcerative and lichenoid lesions, which were refractory to topical corticosteroids. The oral lesions were concomitant to nivolumab-induced adrenal insufficiency. These adverse events led to nivolumab discontinuation, which favored oral lesion healing and adrenal insufficiency remission. Through a brief review of the literature concerning nivolumab toxicity in the oral cavity, we discuss the clinical aspect and management of these lesions.

Severe progressive scarring pembrolizumab-induced lichen planopilaris in a patient with metastatic melanoma.

Lichenoid reactions are one of the many cutaneous immune-related adverse events seen with the use of immune checkpoint inhibitors, particularly anti-PD1 inhibitors. We present a rare care of severe lichen planopilaris secondary to pembrolizumab, with progression even after cessation of immunotherapy. It is important to recognise the significant long-term impact of these cutaneous adverse effects on patient's quality of life.

Observer agreement in the diagnosis of oral lichen planus using the proposed criteria of the American Academy of Oral and Maxillofacial Pathology.

BACKGROUND: Oral lichen planus (OLP) is a common chronic inflammatory condition with an undefined malignant transformation potential. There have been many attempts at providing a specific definition of OLP without conclusive outcomes. A new set of diagnostic criteria was proposed in 2016 by the American Academy of Oral and Maxillofacial Pathology (AAOMP) in an endeavour to resolve this issue, and this has not yet been evaluated. This study aimed to assess the utility of AAOMP proposed criteria for the diagnosis of OLP. METHODS: Five pathologists blindly assessed a cohort of 215 digital whole slide images (WSI) obtained from haematoxylin and eosin-stained microscopic slides. Forty-six WSI were included twice to assess the intra-observer agreement. Included cases were diagnosed clinically as either OLP or oral lichenoid reaction. Each pathologist was asked to utilize the AAOMP histopathological criteria while assessing slides. The variations in diagnoses were assessed by unweighted kappa statistics. RESULTS: The level of intra-observer agreement was very good (0.801 to 0.899). The level of inter-observer agreement among the observers varied from good (0.658) to very good (0.842) when the responses were categorized as evident/compatible OLP versus no OLP and was good (0.62 to 0.725) when the responses were categorized as evident OLP, versus compatible OLP, versus no OLP. The clinico-pathological correlation was 87.6%. CONCLUSION: A reliable level of agreement can be achieved by pathologists for the diagnosis of OLP using the AAOMP criteria for differentiation between lichenoid and other conditions. There are still limitations in discriminating OLP from oral lichenoid lesions microscopically.