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In dermatology, lichenoid describes lesions with a violaceous hue that is a clinical reflection of basal cell damage in the epithelium and dense mononuclear infiltrate in the sub-epithelium. The violaceous color results from pigment incontinence due to basal cell damage and the Tyndall effect. Although classically described in lichen planus, a lichenoid hue is noted in the oral mucosa in several other disorders that often lead to diagnostic dilemmas. Early and accurate diagnosis is important for the appropriate management of the underlying condition and prognostication. Dermatologists play a central role in managing such patients since, apart from the oral mucosa findings, the cutaneous features also help to significantly differentiate various conditions. Mimickers of oral lichen planus include nicotine stomatitis, oral submucous fibrosis, oral lichenoid lesions, mucosal discoid lupus erythematosus, pemphigus vulgaris, paraneoplastic pemphigus, mucous membrane pemphigoid, fixed drug eruption, plasma cell cheilitis/gingivitis, and erythema multiforme. While a detailed history and clinical examination can help reach a diagnosis in most cases, histopathology, immunofluorescence, and other relevant investigations help establish the diagnosis., (© 2024 the International Society of Dermatology.)

A healthy 14-year-old boy presented with a 2-month history of two slowly expanding asymptomatic lesions on his right trunk. No etymology of any new medications, recent travel, or tick bites was reported. Physical examination demonstrated two 4.5×2.5- cm and 3.5×2-cm annular hyperpigmented plaques with slightly elicited red borders on the right lower abdomen and right inferior flank. No evidence of atrophy or sclerosis was noted (Figure 1A). A 4-mm punch biopsy revealed irregular epidermal hyperplasia with alteration of thinned and quadrangular rete ridges, a dense band-like lichenoid infiltrate in the papillary dermis admixed with numerous melanophages and occasional necrotic keratinocytes. No evidence of epidermotropism was observed (Figure 1B). The dermal infiltrate was predominantly composed of CD3+ T-lymphocytes admixed with rare CD20+ B-lymphocytes and increased CD8-CD4 ratio. The patient showed significant improvement following the application of a potent steroid ointment for several weeks.

Objective: Oral lichen planus (OLP) is an immune-mediated condition featuring chronic inflammation. The World Health Organization classifies OLP as potentially malignant, but it is believed that the malignant transformation of OLP occurs in lesions with both lichenoid and dysplastic features (LD). This review discusses the issues surrounding OLP and LD, including their malignancy, classification, and categorization, and whether lichenoid inflammation causes dysplastic changes in LD or vice versa., Methods: English full-text literature on OLP, LD and/or dysplasia was retrieved from PubMed, CINAHL, and Google Scholar., Results: Thirty-six publications including original research articles, reviews, meta-analyses, books, reports, letters, and editorials were selected for review., Discussion: Research suggests that OLP has malignant potential, although small, and that LD should not be disregarded, as dysplasia presenting with or without lichenoid features may develop into cancer. There is also disagreement over the classification and categorization of LD. Different terms have been used to classify these lesions, including lichenoid dysplasia, OLP with dysplasia, and dysplasia with lichenoid features. Moreover, in LD, it is not clear if dysplasia or lichenoid infiltration appears first, and if inflammation is a response to dysplasia or if dysplasia is a response to the persistent inflammation. The main limitation in the literature is the inconsistency and subjective nature of histological diagnoses, which can lead to interobserver and intraobserver variation, ultimately resulting in the inaccurate diagnosis of OLP and LD., Conclusion: Although further research is required to understand OLP and LD, both lesions should be considered potentially malignant and should not be disregarded., Competing Interests: The authors have declared no conflicts of interest., (Copyright © 2024 CDHA | ACHD.)

Evaluating the association of ABO blood group with different delayed hypersensitivity reactions, such as oral lichenoid reaction (OLR), can provide a new perspective for clinical practice. Therefore, this study designed to investigate ABO blood group antigens in OLR patients. In this case-control study, the ABO blood group of 112 OLR patients and 117 individuals without oral lesions were included. Gender, age, characteristics of the lesions, medications and restorative materials recorded. Chi-square test used to compare the frequency of ABO blood groups in OLR patients with controls. The O blood group was significantly higher in OLR patients and all its subtypes. Also, there were significant relation between O blood group, and severity of lesions. The frequency of dysplasia was non-statistically significant higher in OLR patients with O blood group than other blood group. Based on the results of the present study, O blood group was significantly more in patients with lichenoid reaction than control group, and AB blood group was the lowest. Also, O blood group showed a positive association with the more severe form of OLR lesions and frequency of dysplasia., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

We analyzed records of 30 patients with lichen striatus (age < 18 years) in this retrospective study. Seventy percent were females and 30% were males with a mean age of diagnosis of 5.38 ± 4.22 years. The most common age group affected was 0-4 years. The mean duration of lichen striatus was 6.66 ± 4.22 months. Atopy was present in 9 (30%) patients. Although LS is a benign self-limited dermatosis, long-term prospective studies with a greater number of patients will help in better understanding of the disease including its etiopathogenesis and association with atopy., (© 2023 Wiley Periodicals LLC.)

Annular lichenoid dermatitis of youth (ALDY) is a newly described controversial benign lichenoid inflammatory cutaneous disorder often characterized by annular patches with hypopigmented center and surrounding erythematous border. Primarily, it affects the trunk and groin of young patients. Since its first description in 2003, additional patients have been reported, leading to better characterization of the entity; nevertheless, the pathogenesis is still unclear, and several hypotheses have been provided about possible triggering or causative factors. It tends to follow a chronic course, with some lesions spontaneously remitting, while others may be persistent or recur post-treatment. No standard validated treatment has been indicated so far for this disorder. Commonly prescribed topical treatment includes corticosteroids and calcineurin inhibitors with variable response.

Lichenoid dermatitis can be a perplexing entity encompassing an array of cutaneous disorders. Two hundred forty-three (243) cases of otherwise unclassifiable lichenoid dermatitis were examined histologically employing a special cytokeratin stain. Occult squamous cell carcinoma was detected in three of the 243 cases, uncovered by special immunohistochemistry staining within histologic specimens of lichenoid dermatitis. We recommend staining for cutaneous cancer becoming a routine practice in evaluating cutaneous lichenoid dermatitis., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Background: Distinguishing melanocytic pseudonests encountered in lichenoid dermatoses or lichenoid keratoses from melanoma in situ (MIS) with brisk lichenoid inflammation can prove challenging., Methods: We designed a case-control study to evaluate the accuracy metrics of PRAME immunohistochemistry to distinguish melanocytic pseudonests in lichenoid dermatoses or keratoses from inflamed MIS. Immunostaining for PRAME was performed on paraffin-embedded formalin-fixed diagnostic tissue using a rabbit monoclonal antibody to PRAME (Abcam), with a 1:3200 dilution on a Leica Bond detection system., Results: Our search identified 21 cases of melanocytic pseudonests (n = 21, 46%) encountered in lichenoid dermatoses and 24 cases of inflamed MIS (n = 24, 53%). Each method of evaluating PRAME immunohistochemistry (PRAME+ clusters, PRAME % of melanocytes by four categories and PRAME+ melanocyte counts per linear mm of epidermal basal layer) showed statistically significant differences between the MIS and the pseudonest cohorts (respectively, p < 0.001; p < 0.001; and p < 0.001). Receiver operating characteristics analysis for PRAME+ melanocyte counts per linear mm of epidermal basal layer revealed an area under the curve of 0.9 ± 0.05 (95% confidence interval 0.9-1.0). When determining an optimal cut-off point for the best Youden index [sensitivity (%) + specificity (%) - 100], the cut-off of 1.0 PRAME+ melanocytes per linear mm showed a sensitivity of 79.2% and specificity of 85.7% (Youden index 0.65) to distinguish MIS from pseudonests., Conclusion: PRAME immunohistochemistry may constitute an additional tool for this challenging differential diagnosis., (© 2023 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Introduction: Imatinib Mesylate (IM), a tyrosine kinase inhibitor, has been reported to cause several adverse reactions, most of them with cutaneous involvement. Non- Lichenoid IM associated skin reactions have been sufficiently- recorded. To our knowledge, Lichenoid Drug Eruption (LDE) is recorded in a minority of registries., Case Report: To describe an LDE induced case by IM treatment., Treatment and Outcome: Histological Confirmation and promptly dermatological consultation relieved successfully the cutaneous adverse event., Discussion: Ongoing expansion of IM usage in a wide spectrum of new indications is more likely to make physicians experience such LDE cutaneous side effects more often. Hence, they should be highly suspicious to early detect these distinct histologic entities, handle these undesired complications and guarantee satisfactory immediate outcomes, avoiding frivolous IM dosage modifications.

Background: Oral lichen planus (OLP) and oral lichenoid lesions (OLL) comprise a group of oral mucosal disorders that have similar clinical and histological features., Objectives: To compare the levels of investigated biomarkers in biopsied OLP and OLL, and to determine the pattern of biomarkers, which could be useful for the biological characterization of these 2 disorders., Material and Methods: A total of 56 biopsy specimens in 2 groups were analyzed in this study. One group consisted of 25 idiopathic OLP lesions, and the other included 31 OLL from patients treated with antihypertensive and cardiac medications. The expression of protein p53, topoisomerase I (topo I), heat shock protein 90 (HSP90), and E-cadherin was analyzed using immunohistochemistry., Results: The p53 protein expression showed a trend to a positive correlation with topo I expression in the total sample (p = 0.067, R = 0.25). The p53 protein and HSP90 expression was higher in the OLL group compared to the OLP group, but the difference was not statistically significant. No association was found between topo I and E-cadherin expression for either the OLP or OLL group., Conclusions: The findings of this study suggest that the slightly higher protein p53 and HSP90 expression in the OLL group might be caused by the medications used. The slight association between p53 and topo I expression indicates that the cooperation between these proteins might be essential for the growth of OLP/OLL in general. We conclude that the overexpression of p53 protein and high expression of topo I found in both types of lesions might induce their biologically aggressive behavior.

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., (© 2022. The Author(s).)

Background: The diagnosis of oral lichenoid lesions (OLL) remains a challenge for clinicians and pathologists. Although, in many cases, OLL cannot be clinically and histopathologically distinguishable from oral lichen planus (OLP), one important difference between these lesions is that OLL has an identifiable etiological factor, e.g. medication, restorative material, and food allergy. The list of drugs that can cause OLL is extensive and includes anti-inflammatory drugs, anticonvulsants, antihypertensives, antivirals, antibiotics, chemotherapeutics, among others. This work aimed to perform a literature review of OLL related to chemotherapy drugs and to report two cases of possible OLL in patients with B-cell and T-cell non-Hodgkin lymphomas in use of chemotherapy and adjuvant medications. We also discuss the challenge to clinically and histopathologically differentiate OLL and OLP., Case Presentation: In both cases, oral lesions presented reticular, atrophic, erosive/ulcerated, and plaque patterns. The diagnosis of OLL was initially established in both cases by the association of histopathology and history of onset of lesions after the use of medications. Although the patients have presented a significant improvement in the oral clinical picture for more than 2 years of follow-up, they still have some lesions., Conclusion: A well-detailed anamnesis associated with the drug history, temporal relationship of the appearance of the lesions, and follow-up of patients are fundamental for the diagnosis of OLL related to drugs. Nevertheless, its differentiation from OLP is still a challenge., (© 2022. The Author(s).)

Annular lichenoid diseases encompass a diverse range of pathologies that present as circular, raised, or flat lesions that may vary in size and number. Examples include annular lichenoid dermatitis of youth, annular lichen planus, erythema dyschromicum perstans, erythema multiforme, fixed drug eruption, lichen sclerosus, neonatal lupus, porokeratosis, subacute cutaneous lupus erythematosus, and lichenoid syphilis. Clinical morphology and histopathology can differentiate these entities., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Background: This study assessed the efficacy of using oral liquid-based brush cytology (OLBC) coupled with immunostained cytology-derived cell-blocks, quantified using machine-learning, in the diagnosis of oral lichen planus (OLP)., Methods: Eighty-two patients diagnosed clinically with either OLP or oral lichenoid lesion (OLL) were included. OLBC samples were obtained from all patients before undergoing surgical biopsy. Liquid-based cytology slides and cell-blocks were prepared and assessed by cytomorphology and immunocytochemistry for four antibodies (Ki-67, BAX, NF-κB-p65, and AMACR). For comparison purposes, a sub-group of 31 matched surgical biopsy samples were selected randomly and assessed by immunohistochemistry. Patients were categorized according to their definitive diagnoses into OLP, OLL, and clinically lichenoid, but histopathologically dysplastic lesions (OEDL). Machine-learning was utilized to provide automated quantification of positively stained protein expression., Results: Cytomorphological assessment was associated with an accuracy of 77.27% in the distinction between OLP/OLL and OEDL. A strong concordance of 92.5% (κ = 0.84) of immunostaining patterns was evident between cell-blocks and tissue sections using machine-learning. A diagnostic index using a Ki-67-based model was 100% accurate in detecting lichenoid cases with epithelial dysplasia. A BAX-based model demonstrated an accuracy of 92.16%. The accuracy of cytomorphological assessment was greatly improved when it was combined with BAX immunoreactivity (95%)., Conclusions: Cell-blocks prepared from OLBC are reliable and minimally-invasive alternatives to surgical biopsies to diagnose OLLs with epithelial dysplasia when combined with Ki-67 immunostaining. Machine-learning has a promising role in the automated quantification of immunostained protein expression., (© 2022 The Authors. Journal of Oral Pathology & Medicine published by John Wiley & Sons Ltd.)

Lichenoid tissue reaction/interface dermatitis represents a class of mucocutaneous inflammatory diseases which share common histopathological manifestations. One patient presented to our clinic whose oral lesions could not categorized into a definitely clinical or pathological diagnosis, but could be ascribed to lichenoid tissue reaction/interface dermatitis with moderate-to-severe dysplasia. Photodynamic treatment was applied in this case and a satisfactory result was eventually achieved. Signs of recurrence were not revealed at the follow-up of the tenth month., (Copyright © 2022 Elsevier B.V. All rights reserved.)

The clinicopathological features that precisely characterize oral lichen planus (OLP) and oral lichenoid lesions (OLL) still represent a challenge. The aim of the present study was to analyze, from an oral pathologist perspective, the clinical features from OLP and OLL. Specimens fullfilling the histological criteria for OLP and OLL, and also compatible with OLP (OLP-C), were selected and clinical information was retrieved from the laboratory forms. The final sample was composed by 221 cases, including 119 OLP (53.8%), 65 OLP-C (29.4%) and 37 OLL (16.7%). Females were more affected in the three groups, but the number of males was higher in OLL. Mean age was lower in OLP (52.3 years) in comparison with OLL (57.9 years) (p=0.020). Buccal mucosa and tongue involvement was more frequent in OLP; gingival involvement was uncommon in OLL. The reticular pattern was more frequently found in OLP, while the association of reticular and atrophic/erosive/ulcerated patterns was more common in OLP-C and OLL (p=0.025). In conclusion, gender and mean age of the patients, and anatomical location and clinical manifestation of OLL are different from OLP, and could help to better characterize this group of conditions. Specimens diagnosed as OLP-C showed clinical parameters close to OLP.

The widespread use of PD-1 inhibitors to treat various solid tumors has brought certain challenges for the clinician, including immune-related adverse events (irAEs). Cutaneous toxicities are among the most observed irAEs. Bullous and lichenoid dermatoses following PD-1 inhibitor therapy have been described. Here we report a novel case of lichen planus pemphigoides, featuring characteristics of both bullous pemphigoid and lichen planus, in a patient treated with nivolumab for renal cell carcinoma. We subsequently review all three cutaneous conditions which may arise in the context of PD-1 inhibitor therapy., (© 2022 The Authors. Dermatologic Therapy published by Wiley Periodicals LLC.)

Introduction: Oral lichen is a chronic inflammatory disease for which diagnostic management and follow-up are heterogeneous given the absence of specific guidelines in France. Our objective was to develop French multidisciplinary guidelines for the management of oral lichen., Materials and Methods: Working groups from the Groupe d'Etude de la Muqueuse Buccale (GEMUB) formulated a list of research questions and the corresponding recommendations according to the "formal consensus" method for developing practice guidelines. These recommendations were submitted to a group of experts and the degree of agreement for each recommendation was assessed by a scoring group., Results: Twenty-two research questions, divided into 3 themes (nosological classification and initial assessment, induced oral lichenoid lesions, and follow-up) resulted in 22 recommendations. Initial biopsy for histology is recommended in the absence of reticulated lesions. Biopsy for direct immunofluorescence is recommended for ulcerated, erosive, bullous types and for diffuse erythematous gingivitis. Management should include a periodontal and dental check-up, and investigation for extra-oral lesions. Hepatitis C testing is recommended only if risk factors are present. Definitions, triggering factors and the management of "induced oral lichenoid lesions" were clarified. Oral lichen must be monitored by a practitioner familiar with the disease at least once a year, using objective tools., Conclusion: This formalised consensus of multidisciplinary experts provides clinical practice guidelines on the management and monitoring of oral lichen., (Copyright © 2021 Elsevier Masson SAS. All rights reserved.)

Thymomas are neoplasms associated with paraneoplastic disorders. Severe hypersensitivity reactions involving the oral cavity may be the first sign of an undiagnosed thymoma. Oral manifestations of an underlying thymoma may present as recurrent severe painful lesions with associated significant morbidity, often not responding to standard therapeutic measures. This case report describes the treatment of a 75-year-old woman who presented with severe oral lichenoid hypersensitivity reactions secondary to an undiagnosed underlying thymoma. No substantial improvement of the oral conditions was achieved with conventional therapies (topical and systemic steroids); however, almost complete resolution of the lesions was achieved following completion of radiation therapy for the thymic neoplasm. This article is intended to serve as a resource for clinicians to understand early, rare manifestations of an undiagnosed thymoma., Competing Interests: The authors report no conflict of interest pertaining to any of the topics discussed in this article.

Background: Tattooing has been around for many years and is becoming an increasingly common fashion trend. As there are often few regulatory laws regarding the practice, an increase in the incidence of cutaneous reactions to tattoo inks is noted. These include allergic reactions, granulomatous dermatitis, infections, lichenoid dermatoses, and sometimes malignancy. The present study examines the histopathological changes seen in patients with cutaneous reactions to tattoo ink., Method: A prospective observational study was conducted over 18 months in the dermatology clinic of a tertiary care center in western India. The study population included 22 patients with cutaneous reactions over the tattoos. Punch biopsy specimens were sent to study the pattern of histopathological response., Results: All 22 patients studied were between the ages of 17 and 35 years. The mean duration of development of reaction was 8.1 months. Most of the reactions were seen in black ink tattoos performed by amateurs. Perivascular and spongiotic dermatitis suggestive of allergic response was the most common feature on histopathology. Granulomatous response and lichenoid response were seen in five and three biopsies, respectively., Conclusion: Legalization is needed for this practice to prevent tattoo reactions. Histopathological evaluation is important as tattoo reactions may be associated with skin infections and malignancies., (© 2021 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

The lichenoid tissue reaction pattern generally signifies cytotoxic damage to the epithelium. When such reaction pattern occurs on vulvar skin or mucosa, the effects can result in considerable morbidity. None of the entities discussed in this review are entirely unique to the vulva, however, some entities may classically occur at this site, while others tend to be widespread diseases that may incidentally affect vulvar skin and mucosa. Given the complex anatomy of the vulva and the bridging of a site showing both keratinizing squamous epithelium and non-keratinizing squamous mucosa, histopathologic features may display variation in presentation. Although identification of a "lichenoid reaction pattern" alone may provide insight into the disease process, understanding of clinical presentation and specific sites of involvement, along with recognition of the nuanced features of the disease entities can help establish a specific diagnosis. Accurate histopathologic diagnoses by pathologists can improve the ability for treating clinicians to implement timely and effective treatment., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Drug reactions are among the most common reasons for inpatient dermatology consultation. These reactions are important to identify because discontinuation of the offending agent may lead to disease remission. With the rising use of immunomodulatory and targeted therapeutics in cancer care and the increased incidence in associated reactions to these drugs, the need for accurate identification and treatment of such eruptions has led to the development of the "oncodermatology" subspecialty of dermatology. Immunobullous drug reactions are a dermatologic urgency, with patients often losing a significant proportion of their epithelial barrier; early diagnosis is critical in these cases to prevent complications and worsening disease. Lichenoid drug reactions have myriad causes and can take several months to occur, often leading to difficulties identifying the offending drug. Fixed drug eruptions can often mimic other systemic eruptions, such as immunobullous disease and Stevens-Johnson syndrome, and must be differentiated from them for effective therapy to be initiated. We review the clinical features, pathogenesis, and treatment of immunobullous, fixed, and lichenoid drug reactions with attention to key clinical features and differential diagnosis., (Copyright © 2020. Published by Elsevier Inc.)

The differential diagnosis between lichenoid drug eruption (LDE) and lichen planus (LP) is difficult due to similar clinical and histological signs but important for treatment and prognosis. The purpose of this study was to propose the new diagnosis method for differentiate LDE from LP. During 2015-2018, 20 patients with confirmed LDE, 13 patients with LP and 134 controls were examined and treated at the Lenoblcenter. All enrolled patients were underwent the injection of 0.5 mL of the 2% lidocaine solution by insulin syringe into the papule with following histological examination. The formation of a blister (bulla) at the site of injection was considered a positive test result. Among LDE, 18 of 20 patients were found positive for developing blister (bulla) and two results were questionable. In 12 of 13 LP patents, bulla on the site of injection was not identified and the result of one patient was nonspecific. All control patients were negative for the proposed test. The histological sections showed that the bulla has corresponded to the separation of the epidermis from the dermis. Intracutaneous injection of 0.5 mL of lidocaine into the papule is an easy highly specific and sensitive method to differentiate LDE from LP., (© 2020 Wiley Periodicals LLC.)

Allergic contact hypersensitivity reactions of the oral mucosa pose a significant medical concern for some patients. Oral hypersensitivity reactions can result from a vast number of allergenic chemicals, but occur commonly from dental materials, flavorings, and preservatives. Clinical presentation is varied and often overlaps with other oral conditions, complicating their diagnosis and management. The most common clinical entities associated with oral hypersensitivity reactions are oral lichenoid reactions and allergic contact cheilitis. In addition to reviewing these conditions and their most common corresponding allergens, this article summarizes the pathogenesis of oral hypersensitivity reactions and addresses patch testing pearls., Competing Interests: Disclosure The authors have nothing to disclose., (Published by Elsevier Inc.)