Abstract
Thirty-seven cases of oral lichen planus (OLP) were investigated clinically, histologically, and immunohistochemically to examine the early characteristics of malignant transformation. OLP was clinically classified into 4 types: reticular (12 cases), erosive/ulcerative (21 cases), leukoplakic (3 cases), and erythroplakic (1 case). In 3 cases of erosive/ulcerative OLP, squamous cell carcinoma (SCC) coexisted. Histologically, the degree of epithelial thickening, subepithelial cell infiltration, cellular atypism, and liquefaction of the basal cell layer were more prominent in erosive/ulcerative type, especially in cases with coexisting SCC, than in reticular type. The proliferating potential of epithelial cells was immunohistochemically investigated using monoclonal antibodies to proliferating cell nuclear antigen (PCNA) and epidermal growth factor receptor (EGFR). Generally, the staining intensities of PCNA and EGF-R in OLP were not so different from those in the healthy oral mucosa. However, an increase of PCNA-positive cells was observed in some cases of erosive/ulcerative OLP, including 3 cases with SCC. The binding of the epithelium to 3 lectins, concanavalin A (Con A), soy bean agglutinin (SBA) and wheat germ agglutinin (WGA) was examined. In healthy oral mucosal epithelia, the binding to each lectin was weak in the basal cell layer and strong in the prickle cell layer. In OLP, bindings to the 3 lectins, especially to WGA, were decreased most prominently in the upper prickle cell layer. The strongest decrease in lectin binding was observed in erosive/ulcerative type. Conversely, Con A binding to the horny cell layer was increased in OLP.
These results suggest that OLP, especially erosive/ulcerative type, has the potential to undergo malignant transformation. Therefore, extensive and prolonged follow up is necessary for this type of OLP.
