Histopathological Classifications of Oral Leukoplakia and its Relation to Cell Proliferative Activity: A Case Series

This study relates the average number of nucleolar organizing regions (NORs) obtained in a series of cases of oral leukoplakia, with three methods of histopathological classification of such lesion.

This is a histopathological-histochemical laboratory cross-sectional study. The 18 cases of leukoplakia analyzed were filed at Pathology Service of the Biological Sciences Institute of the University of Passo Fundo, Rio Grande do Sul, Brazil (SDH/ICB/UPF) (2017 and 2018), from which epidemiological data were extracted. New histological sections were performed for impregnation by the argyrophilic nucleolar organizer regions (AgNOR) technique. The histopathological slides were analyzed by photon microscopy (1,000×), and the nuclei of 100 epithelial cells were photographed to count the number of NORs. Three methods were used for the lesions' histopathological classification [World Health Organization (WHO), Brothwell, and binary system]. The means of NORs were compared with the three histopathological classifications by means of the t or analysis of variance (ANOVA) statistical tests, at a significance level of 5%.

According to the WHO classification method, most cases (11-61.1%) had a moderate classification. Evaluations by the Brothwell method showed moderate and mild classification in 50 and 38.9% of cases, respectively. According to the binary system, most cases (10-55.6%) had low risk. The average NORs found in 100 nuclei of each of the 18 lesions ranged from 2 to 4. When crossing the average NORs with the histopathological classification methods of the lesions by means of the t test or ANOVA, no significant relationship was noted.

The average of NORs is not associated with the histological classifications of leukoplakias. Thus, the AgNOR method should be used with caution when differentiating different histological grades of leukoplakias.

The AgNOR method should be used with caution to determine the clinical treatment of oral leukoplakias, since no agreement was observed between this method and the histopathological classifications available for such lesion.