Lichen planus is a chronic mucocutaneous T cell mediated disease that usually involves the oral mucosa [
The WHO criteria (1978) for histopathological diagnosis of OLP include thickened ortho- or parakeratinised epithelium, liquefaction degeneration of basal layer, well-defined juxtaepithelial lymphocytic infiltration, and Civatte bodies in basal epithelium and lamina propria [
Oral lichenoid reactions are clinical and histological analogues to oral lichen planus. They appear as white hyperkeratotic thickened lesions often related to drugs, dental restorative materials, graft versus host disease, and medications. These lesions occur in atypical sites that usually has straight topographic relation to the causative agent. Similar to oral lichen planus, the lichenoid reactions also occur in various forms like erythematous, reticular, plaque-like, and atrophic [
Histopathologically oral lichenoid reactions show more diffuse subepithelial inflammatory infiltrate which extends much below into the connective tissue and is more lymphohistiocytic compared to mixed inflammatory infiltration [
Mast cells are granular, bone-marrow derived, mobile leucocytes with wide range of functions including inflammation, immune modulation, tissue repair, and remodelling. On response to immunologic and nonimmunologic stimuli, they release preformed mediators, vasoactive amines, cytokines, and enzymes via granules [
Antigenically altered basal epithelial cells stimulate the mucosal mast cells through RANTES. Stimulation of mast cells presents the antigen to the T cells which in sequence causes activation and degranulation of mast cell and release of various factors like TNF-
One of the important causes for oral lichenoid reactions could be allergic hypersensitivity reaction in which main causative phenomena occur by degranulation of mast cells [
The present study was designed for quantifying mast cells in oral lichenoid reactions and oral lichen planus to understand the potential function of mast cells in the pathogenesis of these diseases.
The current study involved formalin-fixed paraffin-embedded tissue sections of histopathologically diagnosed cases of oral lichen planus (
Photomicrograph of the section shows normal buccal mucosa (H&E 10x).
Photomicrograph of the section shows parakeratotic stratified squamous epithelium with juxtaepithelial band of inflammatory infiltration in oral lichen planus (H&E 10x). The arrows refer to juxtaepithelial band of inflammatory infiltration in oral lichen planus.
Photomicrograph of the section shows parakeratotic stratified squamous epithelium with basal cell degeneration. The arrows refer to inflammatory infiltration extending deep into reticular zone of lamina propria in oral lichenoid reaction (H&E 20x).
Photomicrograph of the section shows normal buccal mucosa (Toluidine Blue 10x). The arrows refer to mast cells.
Photomicrograph of the section shows intact mast cells in oral lichen planus (Toluidine Blue 40x). The arrows refer to intact mast cells in oral lichen planus.
Photomicrograph of the section shows intact mast cells in oral lichenoid reaction (H&E 40x). The arrow refers to intact mast cells.
1 gm of Toluidine Blue O (sigma) and 100 mL of 70% alcohol were used to prepare Toluidine Blue stock solution. One percent sodium chloride was freshly prepared and pH was adjusted to 2.0–2.5 using glacial acetic acid. Working solution with pH of 2.3 was prepared with 5 mL of Toluidine Blue stock solution and 45 mL of 1% sodium chloride. The working solution was prepared fresh and was discarded after use each time.
By using rotary microtome, 4
The age group of study samples range from 18 to 70 years. The mean age of the patients in Group I, Group II, and Group II was 29.2 years, 43.2 years, and 43.8 years, respectively. The male: female ratio among Group I, Group II, and Group III was 1 : 1, 1.6 : 1, and 1 : 1.6, respectively. The study sample included 4 different sites, buccal mucosa, tongue, lip, and gingiva. All the normal tissues were from the buccal mucosa. Wickham’s striae were present in 95.2% of oral lichen planus and 57.1% of oral lichenoid reactions which were statistically significant (
Chi-square test.
Variable | Chi-square value |
|
---|---|---|
Wickham’s striae | 8.4 | 0.004 (significant) |
The numbers of mast cells were significantly high in oral lichen planus (mean: 14.98) compared to oral lichenoid reactions (mean: 7.96) and normal oral mucosal tissues (mean: 2.02) (Figure
Comparison of mast cell distribution among study groups using Kruskal–Wallis test.
Group |
|
Mean mast cell count | Range | Standard deviation |
|
---|---|---|---|---|---|
Group I | 10 | 2.02 | 0.9–3.1 | 1.18 |
|
Group II | 21 | 14.98 | 7.9–33.4 | 5.16 | |
Group III | 21 | 7.96 | 1.2–17.4 | 5.04 |
Intergroup comparison of mast cell distribution using Mann–Whitney
S. number | Comparison of groups | Median | Mann–Whitney |
|
---|---|---|---|---|
(1) |
|
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Group II | 14.4 | 368.5 |
|
|
Group III | 6.6 | 72.5 | ||
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(2) |
|
|||
Group III | 6.6 | 188.5 |
|
|
Group I | 1.5 | 21.5 | ||
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(3) |
|
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Group II | 14.4 | 210 |
|
|
Group I | 1.5 | 0 |
Mast cells distribution between study group.
Oral lichen planus is a T cell mediated autoimmune disease in which autocytotoxic CD8+ T cells activate the apoptosis of oral epithelial cells [
Oral lichen planus occurs mainly in adults above 40 years with female predilection [
Our study revealed that mast cell count is increased in OLP compared to OLR thereby guiding us to propose that mast cell count can be used as one of the essential histopathological elements in the differentiation of OLP and OLR.
The authors declare that there are no conflicts of interest regarding the publication of this paper.
The authors are thankful to Dr. C. Ravindran, Professor at and Head of Department of Oral and Maxillofacial Surgery, for providing normal tissue samples towards the completion of this study.