Study of Odontogenic Keratocysts-Flow Cytometric Analysis of Proliferative Activity.

Clinicopathological studies and flow cytometric analyses were performed for 62 cases of odontogenic keratocyst obtained from the file of the Department of Oral and Maxillofacial Surgery, Nihon University School of Dentistry between 1984 and 1998. The Patients ranged in age from 12 to 74 years, and the peak incidence was in the third decade. The male: female ratio was 1.5: 1. Cysts were most frequently found in the third molar region, including the ramus. Most cysts were found incidentally on radiographic examination and appeared as unilocular, smooth bordered, radiolucent lesions. Most lesions were less than 4cm in diameter. Impacted teeth were found in 24 of 70 cysts, and 18.6% of the cysts were associated with root resorption of neighboring teeth. When classified according to the keratin type of the cyst-wall epithelium, most cysts were type II (58.5%).Flow cytometric analysis was performed for lining epithelial cells isolated from paraffin embedded specimens. Nuclear staining was done with Ki-67 antibody. The Ki-67 antigen labeling rate of odontogenic keratocysts was significantly higher (7.9±5.7%) than that of radicular cysts (2.9±1.3%). The number of cysts with a high Ki-67 antigen labeling rate was higher in type III than in the other three groups. We found a significant correlation between the Ki-67 antigen labeling rate on flow cytometry and the Ki-67 antigen positive cell rate on immunohistochemical examination. An advantage of flow cytometric analysis is that it can precisely enumerate proliferating cells of odontogenic keratocysts.