Cell proliferation proteins and aggressiveness of histological variants of ameloblastoma and keratocystic odontogenic tumor

Tumors that originate from the epithelium of the odontogenic apparatus are classified as benign or malignant. The proliferative activity could provide a basis for differences in the biologic behavior among the histological variants of ameloblastoma (AM) and keratocystic odontogenic tumor (KCOT). We examined 32 solid AM and 18 KCOT cases. The AM sample comprised 16 cases of follicular AM, six cases of unicystic AM, eight cases of plexiform AM and two cases of acanthomatous AM. Sections were stained with the Ki-67 antibody. Ten representative fields were selected randomly in each section. For AM, peripheral tall columnar cells of tumor islands/nests/cords were selected. For KCOT, fields were selected in the basal and the suprabasal region of the epithelial lining. We counted the average number of Ki-67 positive cells/field for AM and KCOT. AM exhibited Ki-67 expression in peripheral tall columnar cells, whereas KCOT exhibited Ki-67 expression in the basal and suprabasal layer. No significant difference between AM and KCOT was observed; the cellular proliferative activity varied among the subtypes. No significant difference in Ki-67 expression in acanthomatous, cystic and follicular types of AM was observed, although the plexiform type exhibited significantly higher levels than the other three types. High expression of Ki-67 could be a useful prognostic marker for proliferative activity and a prognostic indicator for recurrence rate of AM and KCOT.