Cystic ameloblastoma - Behavior and treatment of 21 cases

Purpose: This article presents a series of cystic ameloblastomas in which a n unexpected capacity for bony destruction and recurrence was shown. Prolif eration rates were evaluated to see if there is a correlation to the biolog ic behavior of these lesions. Materials and Methods: Clinical and histologic material on 21 consecutive c ystic ameloblastomas was retrieved and reviewed. Immunohistochemical analys is of proliferation-associated Ki-67 protein Was carried out to determine m itotic indices for 10 cystic ameloblastomas, and these were compared to 10 solid ameloblastomas and 10. dentigerous cysts. Results: Lesions from 10 males and 11 females (age range, 12 to 72 years; m ean age, 35 years) were included. All lesions were in the mandible; IS in p osterior sites. Lesion size ranged from 2 to 8 cm in greatest dimension. Co rtical perforation was evident in 7 lesions, and multilocularity (more ofte n in older patients) was evident in 6 lesions. Recurrences were seen in 9 c ases (43%), and the time between initial treatment and recurrence was as lo ng as 10 years. The characteristic histopathologic feature was a thin, stra tified squamous cystic lining with spongiosis and basal palisades. Ten case s also showed mural invasion, and 4 had plexiform luminal proliferation. Th e proliferation rate of the cystic ameloblastomas (represented as a percent age of cells in cell cycle) was 4.3%, compared with solid tumors at 2.8% an d dentigerous cysts at 6.6%. Conclusions: Cystic ameloblastomas occur within a wide age range, but at sl ightly lower mean age than solid lesions. There is a very strong predilecti on for the mandible, and there appears to be no gender difference. Lesions frequently become large, destructive, and/or multilocular. There is a signi ficant recurrence potential, and extended follow-up is advisable. The decep tively innocent histology of cystic ameloblastomas belies the biologic pote ntial of these lesions. The mechanism(s) by which cystic ameloblastomas gai n their destructive behavior seems less likely associated with acceleration of the cell cycle than with other factors. Simple enucleation or currettag e of these lesions may be inappropriate treatment. (C) 2001 American Associ ation of Oral and Maxillofacial Surgeons.