Braz Dent J 23(2) 2012Proliferation and apoptosis in odontogenic tumors 91 INTRODUCTIONAmeloblastoma (AM) is a locally invasive benign epithelial odontogenic tumor that may arise from rests of dental lamina, enamel organ rests, cell rests, the epithelial lining of an odontogenic cyst or from the basal cell layer of oral mucosa (1). Its occurrence varies from 10% to 45.2% of all odontogenic tumors and reaches approximately 1% of all oral cavity neoplasms (2). The usual clinical presentation includes a painless swelling with expansion of the jaws. It can be classified in 3 main groups: solid or multicystic ameloblastoma, unicystic and peripheral. Among these, the solid type is more common and histopathologically represented by follicular, plexiform, acanthomatous, desmoplastic, granular and basal cell patterns (3). A high proliferative activity of the odontogenic epithelium in ameloblastoma (AM) and keratocystic odontogenic tumor (KOT) has been demonstrated. However, no previous study has simultaneously evaluated cell proliferation and apoptotic indexes in AM and KOT, comparing both lesions. The aim of this study was to assess and compare cell proliferation and apoptotic rates between these two tumors. Specimens of 11 solid AM and 11 sporadic KOT were evaluated. The proliferation index (PI) was assessed by immunohistochemical detection of Ki-67 and the apoptotic index (AI) by methyl green-pyronine and in situ DNA nick end-labelling methods. KOT presented a higher PI than AM (p<0.05). No statistically significant difference was found in the AI between AM and KOT. PI and AI were higher in the peripheral cells of AM and respectively in the suprabasal and superficial layers of KOT. In conclusion, KOT showed a higher cell proliferation than AM and the AI was similar between these tumors. These findings reinforce the classification of KOT as an odontogenic tumor and should contribute to its aggressive clinical behavior. Cell Proliferation and Apoptosis in Ameloblastomas and Keratocystic Odontogenic Tumors