HISTOLOGICAL AND IMMUNOHISTOCHEMICAL EVALUATION OF NEW EPITHELIUM AFTER REMOVAL OF ORAL LEUKOPLAKIA WITH ND:YAG LASER TREATMENT

Laser excision has been used with increasing success to treat oral leukoplakia. The aim of the present study was to evaluate whether clinical healing of a leukoplakia after laser surgery is associated with a normal functional status of the new epithelium and whether pathological alterations in these parameters are related to the risk of local recurrence. The study population consisted of 13 consecutive patients with oral leukoplakia in which clinical healing was achieved after laser therapy using an Nd:YAG laser (Model 6000, Laser Sonics, Cooper Laser Sonics). At the end of the therapy, all patients underwent a second biopsy of the clinically healthy tissue. Epithelial cell turnover was evaluated before and after laser surgery by Ki67 protein expression, and positive staining of more than 20% was considered abnormal. All patients were followed on a monthly basis. Eight patients had abnormally high Ki67 values before laser therapy (mean 27.4 ± 6.2%), but the levels decreased significantly after treatment (17.6 ± 8.5%; t = 2.6, p < 0.05). High Ki67 values persisted in three patients, and local recurrences in the new epithelium was observed in two of these patients. Kaplan-Meier statistics showed that the between-group difference was statistically significant (Chi square 7.3; p < 0.01). In conclusion, this is the first prospective study to show that clinical healing of leukoplakia treated by laser surgery may be accompanied by altered cell turnover in 20% of the cases. Ki67, as a marker of proliferative status, may be a prognostic indicator in the mucosa replacing the lesion.