Nucleolar organizer regions (AgNORs) in odontogenic cysts and ameloblastomas.

The aim of this study was to determine whether nucleolar organizer regions (AgNORs) may be of value in distinguishing various odontogenic cysts from the unicystic ameloblastoma. Histological sections were prepared from fifteen cases each of odontogenic keratocyst, residual cyst, dentigerous cyst, unicystic ameloblastoma and conventional ameloblastoma. In each case intra-nuclear AgNOR dots were counted in 100 consecutive basal nuclei. Statistical comparison of the least squares means showed that those areas of unicystic ameloblastomas lined by characteristic epithelium had a significantly lower AgNOR count than the other groups (P < 0.05). The dentigerous cysts had significantly higher AgNOR counts than the residual cysts and unicystic ameloblastomas (P < 0.05). These differences may or may not be indicative of variations in metabolic, proliferative or transcriptional activity. We conclude that AgNOR counts are not of diagnostic significance and cannot be used to distinguish the various odontogenic cysts from one another nor from the unicystic ameloblastoma.