A semi-quantitative assessment of the histopathology of oral lichen planus

Composition of hemidesmosomes in basal keratinocytes of normal buccal mucosa and oral lichen planus

Oral lichen planus (OLP) is a chronic inflammatory disease displaying ultrastructural disturbances in epithelial hemidesmosomes. The expression of several key hemidesmosomal components in OLP as well as in normal buccal mucosa is, however, unknown. The aim of the study was therefore to examine intracellular and extracellular components involved in hemidesmosomal attachment, in OLP (n = 20) and in normal buccal mucosa (n = 10), by immunofluorescence. In normal buccal mucosa, laminin-α3γ2, integrin-α6β4, CD151, collagen α-1(XVII) chain, and dystonin showed linear expression along the basal membrane, indicating the presence of type I hemidesmosomes. Plectin stained most epithelial cell membranes and remained unphosphorylated at S4642. In OLP, most hemidesmosomal molecules examined showed disturbed expression consisting of discontinuous increases, apicolateral location, and/or intracellular accumulation. Plectin showed S4642-phosphorylation at the basement membrane, and deposits of laminin-α3 and laminin-γ2 were found within the connective tissue. The disturbed expression of hemidesmosomal proteins in OLP indicates deficient attachment of the basal cell layer, which can contribute to detachment and cell death of basal keratinocytes seen in the disease.

Programmed cell removal biomarkers calreticulin and CD47 implicated in oral lichen planus

OBJECTIVES

To investigate the expression of the programmed cell removal markers, calreticulin (CRT) and CD47, known to be involved in various autoimmune diseases, in patients with oral lichen planus (OLP), and to investigate the association with clinical behavior.

MATERIALS AND METHODS

Biopsies of 78 patients with OLP were included. The clinical data were collected from patients' charts. The expression of CRT and CD47 was immunomorphometrically analyzed in the epithelial (CRTep, CD47ep) and inflammatory cells (CRTinf, CD47inf), and the results were correlated with the clinical presentation.

RESULTS

The epithelial and inflammatory cells expressed CRT (2.83 ± 6.62 and 5.13 ± 3.72) and CD47 (7.92 ± 4.6 and 10.7 ± 7.16). The expressions of CD47ep and CD47inf were associated (R = 0.64, P < 0.0005) with one another. The expressions of CRTinf and CD47ep were higher in atrophic erosive forms (A/ELP) than in the keratotic form of patients with OLP (6.46 ± 0.76 and 9.38 ± 0.87 vs 4.2 ± 0.61 and 6.84 ± 0.91, respectively, P = 0.002 and P = 0.021). The expression of CRTep was associated with more localized lesions (P < 0.009) and more abundant in males (P = 0.049), and the expression of CRTinf was associated with the presence of skin lesions and symptoms (P < 0.034 and P = 0.047, respectively). Only in A/ELP patients, the expression of CRTep was associated with high expression of CD47ep (R = 0.6, P = 0.004), where both CD47ep and CD47inf were associated with lower age of the patients (R = -0.48, P = 0.03 and R = -0.54, P = 0.01).

CONCLUSIONS

The pattern of expression of CRT and CD47 in OLP suggests a general programmed cell removal response in OLP. Symptomatic patients may benefit from CRT/CD47 targeted therapy in the future.

Metallothionein, a marker of antiapoptosis, is associated with clinical forms of oral lichen planus

OBJECTIVES

To investigate the expression of anti- and proapoptosis markers, metallothionein (MT), and caspase-2, in the epithelial and inflammatory cells of oral lichen planus (OLP) patients, and to investigate the association with clinical parameters.

MATERIALS AND METHODS

Included were biopsies of 70 OLP patients. The clinical data were collected from patients' charts. The expression of MT and caspase-2 was immunomorphometrically analyzed in the epithelial and inflammatory cells, and the results were correlated with the clinical presentation.

RESULTS

The epithelial and inflammatory cells expressed MT (10.2 ± 5.75 and 0.68 ± 0.86) and caspase-2 (1.54 ± 2.6 and 0.98 ± 1.15) which show a trend toward an inverse expression. The expression of MT in the epithelium was significantly higher in patients presenting with keratotic lichen planus than in patients with the atrophic and erosive forms (P = 0.0008). In the inflammatory cells, the expression of MT was inversely correlated with increasing age (R = 0.34, P = 0.0069).

CONCLUSIONS

The pattern of expression of MT and caspase-2 in OLP suggests an extensive antiapoptotic response in the keratotic form of the disease. Symptomatic patients may benefit from therapy targeted to apoptosis in the future.

NGF and its receptors TrkA and p75NTR in the epithelium of oral lichen

BACKGROUND

Nerve growth factor (NGF) can through its receptors TrkA and p75(NTR) convey signals for cell survival, differentiation and death. The aim of this study was to examine whether NGF can play a role in the pathology of oral lichen (OL).

METHODS

Sections from biopsies taken from patients with erythematous (ERY) OL and from volunteers with normal oral mucosa (NOM) were immunostained with antibodies against NGF, proNGF, TrkA, phosphorylated Trk, p75(NTR) and phosphorylated Akt (pAkt) and expression of RNA coding for proNGF/NGF was investigated by in situ hybridization.

RESULTS

Both in ERY OL and NOM, cytoplasmic staining for NGF was seen in granular and upper spinous cell layers of the epithelium, whereas proNGF staining was seen in all epithelial cell layers. In situ hybridization showed that the proNGF protein was produced in the same cell layers. In OL, strong cytoplasmic stainings for TrkA and activated Trk (pTrk) were observed in all epithelial cell layers while these stainings were only weak in NOM. Basal keratinocytes in OL showed no or only weak cytoplasmic staining for p75(NTR), but in NOM there was a clear cell membrane staining. In OL, strong cytoplasmic and intermittent nuclear staining for pAkt was observed in spinous, granular and superficial layers, while basal and parabasal keratinocytes were negative. This staining was weak or absent in the entire epithelium of NOM.

CONCLUSIONS

TrkA upregulation and activation in OL is one of the pathways that can activate pAkt and thereby rescue epithelial cells from untimely cell death.

Survival signalling in keratinocytes of erythematous oral lichen planus

BACKGROUND

Keratinocytes in oral lichen (OL) planus have been shown to be exposed to potentially cell death-inducing factors such as tumour necrosis factor-alpha (TNF-alpha) and FasL, produced by the cells of the inflammatory infiltrate and by the keratinocytes themselves. Mostly, however, the lesions do not show ulceration, the clinical manifestation of substantial keratinocyte death. The aim of this study was to find support for the contention that there is activation of protecting anti-apoptotic mechanisms in keratinocytes in a form of chronic OL (erythematous OL; ERY OL), simultaneously with the pathological cell death signals.

METHODS

Biopsies from patients with normal oral mucosa (NOM) or with ERY OL were compared by immunohistological staining.

RESULTS

In ERY OL keratinocytes, both the pro-apoptotic FADD and the anti-apoptotic molecules p-IKK, NF-kappaB/p50, FLIP(L), cIAP-1 and cIAP-2 were strongly upregulated when compared with NOM. There were no significant differences in the staining patterns for active caspase-3 and caspase-8 with only few positive cells for both enzymes.

CONCLUSIONS

The presently observed marked increase in expression of anti-apoptotic molecules in ERY OL epithelium may counteract the pro-apoptotic assault and rescue the epithelium from rampant cell death and thereby clinical ulceration.

Nitrative and oxidative DNA damage in oral lichen planus in relation to human oral carcinogenesis

Oral lichen planus (OLP) is a chronic inflammatory disease, which has been clinically associated with development to oral cancer. A double immunofluorescence labeling study found that 8-nitroguanine and 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) accumulated in oral epithelium in OLP and oral squamous cell carcinoma (OSCC) biopsy specimens, whereas little or no immunoreactivity was observed in normal oral mucosa. Colocalization of 8-nitroguanine and inducible nitric oxide synthase (iNOS) was found in oral epithelium of OLP and OSCC. Immunoreactivity of 3-nitrotyrosine, which is formed by protein tyrosine nitration and is considered to be a biochemical marker for inflammation, was also observed in oral epithelial cells and colocalized with 8-nitroguanine. Accumulation of p53 was more strongly observed in oral epithelium in OSCC than OLP, whereas there was no p53 accumulation in normal oral mucosa. Our findings demonstrate that iNOS-dependent DNA damage in OLP may lead to p53 accumulation in not only OLP but also OSCC. We conclude that the formation of potentially mutagenic DNA lesions including 8-nitroguanine and 8-oxodG may contribute to the development of oral cancer from OLP.

Inhibition of the Transforming Growth Factor-β/Smad Signaling Pathway in the Epithelium of Oral Lichen

The basal cells in epithelium of the erythematous form of oral lichen display hyperproliferation compared with normal oral mucosa. In this study we examined whether this is associated with disrupted production, activation, or signal transduction of the epithelial growth inhibitor transforming growth factor (TGF) beta1. In situ immunostaining showed that most epithelial cells in normal oral mucosa had nuclear and cytoplasmic Smad4 and phosphorylated Smad2/3, but expressed little or no Smad7. Expression of latency-associated peptide TGF-beta1, latent TGF-beta binding protein 1, TGF-beta type I receptor, and TGF-beta type II receptor was readily seen, but only very little TGF-beta1 was activated. In erythematous oral lichen, basal and lower spinous epithelial layers showed staining for latency-associated peptide TGF-beta1, TGF-beta type I receptor, and TGF-beta type II receptor. A band with scanty staining for these molecules, but with marked staining for active TGF-beta1, was seen in the upper spinous and granular layers. Numbers of epithelial cell nuclei with Smad4 and phosphorylated Smad2/3 staining were significantly reduced in erythematous oral lichen compared with normal oral mucosa. Basal and suprabasal cell layers in erythematous oral lichen showed strong cytoplasmic Smad7 protein staining, but in spinous and granular layers Smad7 was localized to the cell membrane. In situ hybridization showed strong Smad7 mRNA expression in almost all basal keratinocytes in erythematous oral lichen; by contrast, no or occasionally very weak Smad7 mRNA expression was seen in these cells in normal oral mucosa. The observations indicate that inhibition of the TGF-beta/Smad pathway may account for the hyperproliferation of keratinocytes in erythematous oral lichen.

Erythematous and reticular forms of oral lichen planus and oral lichenoid reactions differ in pathological features related to disease activity

BACKGROUND

Common clinical forms of oral lichen planus (OLP) and oral lichenoid reactions (OLR) are erythematous (ERY) or reticular (RET). The purpose of this study was to find histopathological changes that differ between these forms.

METHODS

Epithelial thickness, epithelial proliferation rate, apoptosis, and HLA-DR expression were compared among 10 reticular and 12 erythematous lesions, and 11 normal oral mucosa samples (NOM).

RESULTS

The epithelium in ERY was thinner than in NOM, whereas RET showed values between ERY and NOM. Cell proliferation increased significantly in ERY as compared with RET and NOM, with no difference between RET and NOM. Relative numbers of epithelial cell nuclei displaying visible chromatin condensation were reduced in ERY form.

CONCLUSIONS

The markedly increased cell proliferation in ERY supports the notion that this form displays a higher disease activity as compared to RET. It can therefore be important to study each disease form separately.

Is there a role for tumor necrosis factor-alpha (TNF-alpha) in oral lichen planus?

Oral lichen planus (OLP) is a T cell-mediated inflammatory disease of the oral mucosa. T lymphocytes accumulate within OLP lesions by extravasation from the local microvasculature and subsequent migration to the oral epithelium. Tumor necrosis factor-alpha (TNF-alpha) is a cytokine involved primarily in T cell-mediated immunopathological reactions, and it is implicated in diseases which bear clinical and histological similarities to OLP. This review examines the role of TNF-alpha in the initiation and progression of OLP, and summarises evidence for a key role for TNF-alpha in this disease. A unifying hypothesis for the involvement of TNF-alpha in the immunopathogenesis of OLP is presented. Based on this model, a variety of current therapies are explained and several alternative approaches suggested.

Effectiveness of a low dose of cyclosporine in the management of patients with oral erosive lichen planus

This study investigated the effectiveness of a low-dose cyclosporine rinse used in the treatment of oral erosive lichen planus. Fourteen patients with oral erosive lichen planus provided seven experimental sites treated with cyclosporine and seven control sites treated with a placebo. Participants rinsed with 5 ml (500 mg) of cyclosporine or 5 ml of a placebo for 5 minutes each day over a period of 4 weeks. Cyclosporine blood levels as well as complete blood cell counts with differential and serial multiple analysis were monitored throughout the study. Weekly quantitative measurements of lesion size and character (ulceration, erythema, and reticulation) were recorded with the use of an intraoral grid. Healing was defined as the transition from ulceration to erythema to reticulation or to complete resolution. Pain assessment with the use of a visual analogue scale and a questionnaire pertaining to any side effects of treatment were completed each week. At 4 weeks, a statistically significant difference was observed in lesion healing between the cyclosporine and placebo groups. All experimental sites demonstrated progressive healing with evidence of reduced erythema and ulceration, increased reticulation, and decreased pain scores. In contrast, control sites exhibited minimal change in lesion size or character, and patients reported unchanged or increased pain scores. No significant side effects were reported. Within the parameters of this investigation, topical cyclosporine proved to an effective alternative therapy to currently available medications used in the treatment of oral lichen planus.

Photochemotherapy of oral lichen planus. A controlled study

Photochemotherapy with 8-methoxypsoralen and long-wave ultraviolet light (PUVA) has become a useful alternative in dermatologic therapy. PUVA therapy has been successfully used in the treatment of severe psoriasis and cutaneous lichen planus. The aim of this investigation was to use PUVA in the treatment of oral lichen planus (OLP). Eighteen patients with long-standing, bilateral, and severe OLP of the buccal mucosa participated in the investigation. A dose of 0.6 mg/kg 8-methoxypsoralen was administered orally 2 hours before long-wave ultraviolet light irradiation was done. The patients were randomly assigned to treatment of the left or right side of the buccal mucosa. The irradiation therapy was given 12 times at intervals of 2 to 3 days, and the patients received a total average dosage of 16.5 J/cm2. The results showed that 13 treated sites compared with six control sites responded significantly favorable to PUVA therapy. Two patients dropped out because of side effects that were similar to those seen after whole-body irradiation PUVA treatment. The follow up times was 12 months. The conclusion of this study is that PUVA seems to be effective in the treatment of OLP and should be considered in severe cases of OLP.

Oral lichen planus and chronic liver disease: a clinical and morphometric study of the oral lesions in relation to transaminase elevation

Serum transaminase levels (serum glutamic-oxaloacetic transaminase or serum glutamic-pyruvic transaminase) were found to be altered in 40 (21.39%) of 187 patients with oral lichen planus. The patients with oral lichen planus who had altered transaminase levels were on average older than those without liver disorders and exhibited a higher percentage of erosive lesions (p < 0.05) and tongue involvement. Histologically, no statistically significant differences were noted in the extension of inflammatory infiltration or in connective tissue density; nevertheless, the latter was greater in patients without altered transaminase levels. Finally, among those patients with altered liver test results and erosive lichen planus, serum glutamic-oxaloacetic transaminase and serum glutamic-pyruvic transaminase levels were found to be higher than levels in those patients without erosions. This indicates that behavior of the oral lesions is more aggressive as the degree of liver alteration increases. We emphasize that of the 40 patients with altered transaminase levels (all later proved to reflect chronic hepatitis through complementary diagnostic methods), 28 had hepatitis C virus infection.

Quantitative cellular and nuclear volumetric alterations in epithelium from lichen planus lesions of human buccal mucosa

Patients with oral lichen planus lesions may represent a relatively high risk population for subsequent development of oral cancer. Little is known of the relative effects of chronic inflammation and the process of malignant transformation itself on the histological structure of transforming epithelia. We have assessed cellular and nuclear volumes in defined basal and spinous cells from normal buccal mucosa epithelium, from epithelium associated with a non-specific chronic inflammatory infiltrate and from lichen planus lesions. Normal (N) tissues were obtained from the margins of non-neoplastic buccal mucosa lesions. Inflammatory (INF) lesions were from areas of the buccal mucosa diagnosed clinically as traumatic irritation without ulceration, and lichen planus (LI) lesions were biopsied from areas exhibiting Wickham's striae. Basal and spinous epithelial cells from normal and pathological human buccal mucosa were measured on haematoxylin and eosin-stained sections imaged through a video camera using a Zeiss VIDAS analyser and from these measurements, nuclear (VN) and cellular (VCELL) volumes were determined. VN and VCELL derived for both basal and spinous strata were similar in N and INF groups but were almost doubled in the LI group. Comparisons between LI and all other groups were significantly elevated. The effects of the inflammatory infiltrate on the oral epithelium in lichen planus and in non-specific inflammation thus differ significantly. VN and VCELL may serve as potential discriminators between benign lesions and premalignant lichen planus.

Serologic and molecular analysis of the HLA system in Israeli Jewish patients with oral erosive lichen planus

Oral erosive lichen planus is a distinct subtype of the common dermatosis lichen planus. Although the etiology of lichen planus is still obscure, it is known that cell-mediated immune mechanisms and genetic factors underlie its pathogenesis. Previous studies have found an association between lichen planus and HLA-DR3 or DR9 in different population groups. The present work was designed to elucidate, at the serologic and molecular levels, whether and which HLA genes are associated with oral erosive lichen planus in Israeli Jewish patients. A significant association with HLA-DR2 (RR = 4.7; pc < 0.0013) and a decrease in DR4 (RR = 0.3; p < 0.03) among the patients were noted. Oligotyping of DR2 alleles showed the presence of all three common variants (DRB1*1501, DRB1*1502 and DRB1*1601) in the patients, although none of the variants was overrepresented significantly. Three possible explanations for the role of HLA genes in the predisposition to oral erosive lichen planus are discussed. The most attractive theory for the pathogenesis of the disease seems to include the involvement of non-classical HLA genes.

Suppressor cell function in oral lichen planus

Oral lichen planus (OLP) is a common inflammatory condition of the oral mucous membranes which affects between one and two percent of the general population. In accordance with the protracted clinical course of OLP and its association with known auto-immune diseases, the level of self-tolerance is questionable and possibly diminished in patients with this disorder. Normal suppressor T lymphocyte function is reputedly an essential element in the maintenance of self-tolerance, and deficient cell-mediated suppressor activity is implicated in the pathogenesis of auto-immune diseases. For assessment of in vitro cell-mediated suppressor activity in OLP, peripheral blood mononuclear cells (PBMC) from ten patients with OLP and from 11 control subjects were activated with the plant mitogen concanavalin A (Con A), followed by co-culture with autologous responder cells. The ability of irradiated Con A-activated cells to suppress the proliferation of Con A-stimulated responder cells was determined. Con A-induced suppressor activity of PBMC in the OLP patients was significantly less than that in control subjects (p = 0.001). Results of the present investigation complement previous in vitro findings which provided indirect evidence of deficient cell-mediated suppressor activity in OLP, particularly a decreased proportion of circulating CD4+CD45RA+ lymphocytes and reduced Con A-stimulated PBMC proliferation. The depressed Con A-induced suppressor activity of PBMC in the OLP patients provides direct evidence of deficient in vitro cell-mediated suppressor function in OLP, and suggests that defective cell-mediated suppressor circuits and reduced self-tolerance may be involved in the pathogenesis of this disorder.

Phenotypic and functional analysis of peripheral blood lymphocytes in oral lichen planus

To assess cellular immunity in oral lichen planus (OLP), peripheral blood mononuclear cells (PBMC) were obtained from 19 OLP patients and 30 control subjects. The proportions of circulating CD45RA+ and CD29+ lymphocyte subsets were determined. The proliferative activity of PBMC to the non-specific plant mitogens phytohemagglutinin (PHA) and concanavalin A (Con A) was examined together with the spontaneous proliferative response and the response in the autologous mixed lymphocyte reaction (AMLR). In the OLP group, the proportion of CD4+ CD45RA+ T lymphocytes was significantly less than control subjects and the proportion of CD4+ CD29+ T lymphocytes was increased significantly. The proliferative response to PHA was similar in OLP and controls subjects. Con A-stimulated PBMC proliferation was decreased significantly in the OLP group. Spontaneous PBMC proliferation in patients with non-reticular lesions was significantly less than control subjects. Despite a mildly depressed response in the AMLR in OLP patients, this result was not statistically significant. Results of the phenotypic analysis of peripheral blood lymphocytes indicate a decreased proportion of naive T cells and an increased proportion of primed memory T cells, although the antigen specificity of these memory cells remains to be determined. Results of the functional assays would seem to reflect this phenotypic shift, and as T cells responding to Con A stimulation and in the AMLR possess suppressor-inducer activity, these results may also suggest an association between OLP and defective innate T cell-mediated suppressor circuits.

A clinical study of 205 patients with oral lichen planus

Two hundred and five patients with oral lichen planus were divided into two groups: those with only reticular lesions (group 1) and those with atrophic-erosive lesions with or without concomitant reticular lesions (group 2). A comparative study of the two groups showed that the most commonly affected oral location in both was the buccal mucosa. Lesions of the tongue, gingiva, lip, and palate predominated in group 2. Likewise, chronic liver disease and diabetes were more common in the second group, as was extension of the oral lesions (P less than .001).

Oral lichen planus. A review

Lichen planus is a mucocutaneous disease of unknown etiology which, according to current knowledge, may represent a cell-mediated immunological response to induced antigenic changes in the skin and mucosa. Oral lichen planus (OLP) is a disease of adulthood and as one of the most prevalent diseases affecting the oral mucosa it has been the subject of intensive research during recent years. Ultrastructural and immunohistochemical studies particularly dealing with the subepithelial inflammatory cell infiltrate and its relations to epithelial pathology, the basal cell region and the intraepithelial antigen presenting Langerhans' cells, have contributed vastly to our knowledge of the pathogenesis of OLP. However, the treatment of OLP still remains largely symptomatic because many as yet unknown factors, active in the disease process, still remain to be elucidated.

Absorption of a topical steroid and evaluation of adrenal suppression in patients with erosive lichen planus

This study was designed to investigate the absorption of a topical steroid applied to the gingiva and buccal mucosa of patients with erosive lichen planus and to healthy control patients. In addition, adrenal suppression was assessed by measurements of serum and urine cortisol levels. Ten patients with erosive lichen planus and eight control patients provided urine and blood samples at baseline, day 3, and day 21. After establishment of baseline laboratory values, patients were instructed to apply 500 mg of a 0.05% fluocinonide gel to the gingiva and buccal mucosa three times a day for 3 weeks. Measurements of cortisol levels revealed no significant changes in either the disease or the control group. Although procedures were developed to detect fluocinonide, none of the patients showed evidence of the steroid during the study. It was concluded that the topical application of a fluocinonide gel to the gingiva and buccal mucosa over a 3-week period in patients with erosive lichen planus produced no adrenal suppression.

The association of mucocutaneous lichen planus and chronic liver disease

A possible association between mucocutaneous lichen planus and chronic liver disease has been previously postulated in the medical literature. Despite the frequency with which lichen planus occurs in the oral cavity, little mention of such a relationship has been made in the dental literature. A case of lichen planus occurring in a patient with primary biliary cirrhosis and a review of the subject are therefore presented.

Course of various clinical forms of oral lichen planus. A prospective follow-up study of 611 patients

The course of reticular, papular, bullous, plaque-type, atrophic and ulcerative lesions of oral lichen planus (OLP) was studied in 611 patients. Mean age of the patients was 53 years and two-thirds were women. The patients were followed for periods from 1 to 26 years (mean, 7.5 years). The various clinical types had somewhat different courses. Papular affections were seen mainly in the initial phase and had a transitory course. Ulcerative lesions, although more persistent, also generally showed a short-term course. The atrophic form was fluctuating with many remissions and new-established affections. The plaque-type was a more constant form, but also demonstrated many newly established affections. After a few years, many patients had persistent lesions that no longer included the affections most characteristic of OLP, i.e. the reticular and the papular form. Initial presence of papular affections was associated with ages below 50 and atrophic lesions with ages above 60. Plaque-type affections were seen with a significantly higher frequency among tobacco smokers at the onset of OLP. No other correlation was found between the initial presence, the remission and the development of the different clinical forms and various factors as age, sex, general diseases, medication and tobacco smoking. Treatment with topical steroid and/or antimycotics had no effect on the long-term course of the various clinical forms, and it had no persistent effect on symptoms related to OLP. Complete remission was seen in 17% of the patients, and it showed a reverse association with the initial presence of plaque-type affections. However, complete remission was associated with an initial presence of papular affections.(ABSTRACT TRUNCATED AT 250 WORDS)

Malignant development of lichen planus-affected oral mucosa

The present report describes malignant development in oral lichen planus (OLP) among 611 patients (409 F, 202 M) followed for periods from 1-26 years (mean: 7.5). During follow-up, 9 patients (1.5%), 8 women (1.9%) and 1 man (0.5%) developed oral squamous cell carcinomas (SCC) in areas of lichen planus lesions. The age of the patients at diagnosis of carcinoma ranged from 56-79 years (mean: 70.4) and the length of follow-up before malignant development ranged from 4.9-24 years (mean: 10.1). The estimated number expected to develop oral cancer in a sample of the general Danish population of similar size, age distribution and follow-up was 0.18 (0.11 F, 0.07 M) i.e., OLP cases showed a 50-fold increase (F = 70- M = 14-fold). The observed number of cancer cases was significantly higher than the estimated number (p less than 0.00001). Therefore, oral lichen planus fulfils the WHO criterion of a premalignant condition.

Subsets of T lymphocytes in peripheral blood of patients with oral lichen planus

The T lymphocyte subsets in the peripheral blood were studied in 26 patients with oral lichen planus and in 11 normal controls. Lymphocyte subsets were identified with monoclonal antibodies (Ortho Diagnostic System Inc. Raritan, New Jersey, USA) by an indirect immunofluorescent antibody method. This study shows no significant difference between patients with oral lichen planus and healthy controls. The conclusion is that local immunity, due to the breakdown of skin-associated lymphoid tissue, not a generalized immunologic disorder, is considered to be involved in the pathogenesis of oral lichen planus.

The expression of HLA-DR on keratinocytes in oral lichen planus

HLA-DR is a Class II histocompatibility antigen which has recently been reported to occur in increased amounts in dermal and oral lichen planus. Its expression in epithelium was previously thought to be limited to Langerhans cells. In this study, formalin-fixed sections of oral lichen planus and a variety of other oral mucosal lesions were stained with a monoclonal antibody to HLA-DR using an indirect immunofluorescence test. The expression of HLA-DR by keratinocytes did not appear to be a specific marker for lichen planus as demonstrated by the reactivity of the epithelium in a variety of lesions of the oral mucosa. If HLA-DR expression is considered to be an inducible function, perhaps in response to gamma interferon secreted by activated lymphocytes, then keratinocyte reactivity would not be expected to occur only in lichen planus.