Identification of the AgNORs, PCNA and ck16 proteins in oral lichen planus lesions.

The expression of proliferating cell nuclear antigen (PCNA), cytokeratin 16 (ck16) and Ag nucleolar organizer regions (AgNORs) were assessed in 20 cases of lichen planus, 20 cases of keratosis and 20 cases of normal oral mucosa in order to evaluate the rate of keratinocyte proliferation in these tissues. Three hundred cells were counted in each sample: 100 basal cells, 100 suprabasal cells and 100 squamous cells. The mean number of AgNORs and the percentage of PCNA positive cells were calculated. Except from similar staining of suprabasal cells of lichen planus and keratosis, PCNA and AgNORs values were higher in all layers of lichen planus than in both keratosis and normal oral mucosa. The three groups showed similar ck16 immunostaining: all of the cells were positive, except those of the basal layer. The results suggest that the keratinocyte proliferation index is higher in lichen planus than in keratosis and normal mucosa. Besides, ck16 should not be used to differentiate the entities studied.