UNICYSTIC AMELOBLASTOMA - A REVIEW OF 193 CASES FROM THE LITERATURE

Based on a world-wide literature survey of 193 published cases of unic ystic ameloblastomas (UA), data have been produced allowing the presen tation of a revised concept of this much debated lesion. UA is a varia nt of the solid or multicystic ameloblastoma. Radiographically, the un ilocular pattern is more common than the multilocular, especially in c ases associated with tooth impaction. However, it is stressed that alt hough the lesion is pathomorphologically unicystic, it will far from a lways produce a unilocular radiolucency. The mean age at the time of d iagnosis of UA is closely related to an association with an impacted t ooth. Almost 20 years separate the mean age of the 'dentigerous' varia nt from the 'non-dentigerous' (16.5 years versus 35.2 years) The male: female ratio for the 'dentigerous' type is 1.5:1, but for the 'non-den tigerous' type it is reversed (1.1.8). Location favours greatly the ma ndible (mandible to maxilla = 3 to 13:1). Between 50 and 80% of cases are associated with tooth impaction, the mandibular third molar being most often involved. The 'dentigerous' type occurs on average 8 years earlier than the 'non-dentigerous' variant. The mean age for unilocula r, impaction-associated UAs is 22 years, whereas the mean age for the multilocular lesion unrelated to an impacted tooth is 33 years. Histol ogically, the minimum criterion for diagnosing a lesion as UA is the d emonstration of a single cystic sac lined by odontogenic (ameloblastom atous) epithelium often seen only in focal areas. This simple type of UA (according to the authors' modification of the classification by Ac kermann et al. (Journal of Oral Pathology 1988;17.541-546)), is one of four UA subtypes, the others being (1) simple with intralumenal proli ferations; (2) simple with both intralumenal and intramural proliferat ions; and (3) simple with intramural proliferations only. All four sub types occur in both the 'dentigerous' and 'non-dentigerous' variants. The simple subtype with and without intralumenal proliferations may be treated conservatively (enucleation), whereas subtypes showing intram ural growths must be treated radically, i.e. as a solid or multicystic ameloblastoma. Finally, the authors disclose areas and issues pertain ing to UA. that still need to be addressed. (C) 1998 Elsevier Science Ltd. All rights reserved.