The correlation between epithelial cell proliferation and inflammation in odontogenic keratocyst.

The objective of this study was to investigate the effect of inflammation on Ki-67 and PCNA labeling indices of odontogenic keratocysts. The study included 45 cases of OKC. From each case, three 5-microm sections were cut and stained with hematoxylin and eosin and with monoclonal antibodies for PCNA and Ki-67. In 10 high power fields (HPF), the type of epithelial lining was recorded separately for each field (metaplastic squamous or classic parakeratinized). Labeling indices for Ki-67 and PCNA and the inflammatory infiltrate density in the depth of 1 HPF adjacent to the basement membrane were recorded for each HPF. Parameters were compared between fields, and for each case the average inflammatory score and average labeling indices were calculated, and cases compared. No inflammation was observed in 24.5% of cases, mild in 30.5% and moderate to severe in 45%. Foci of metaplastic non-keratinizing epithelium were observed in 64% of cases, which were twice as common in inflamed cysts (90%) than in non-inflamed cysts (44%). The average labeling indices for PCNA and Ki-67 yielded no significant differences between inflamed and non-inflamed cysts. When compared between HPF's, there was an increase in the Ki-67 labeling index in metaplastic epithelium in areas with moderate to severe inflammation score (p=0.036). PCNA labeling index did not significantly change between areas with low and high inflammation. No differences in labeling indices were observed between areas of classic and metaplastic epithelium with equal inflammation density. A focal increase in Ki-67 expression adjacent to moderate to severe inflammation was found, with no significant effect on the overall proliferation activity of the cysts.