Plexiform unicystic ameloblastoma: a diagnostic problem in dentigerous cysts.

A plexiform pattern of epithelial proliferation, which does not exhibit the histologic criteria for ameloblastoma published by Vickers and Gorlin, occurs in dentigerous cysts. Some pathologists have diagnosed it as ameloblastoma yet others have considered it to be epithelial hyperplasia. Sections of 19 cases and the limited clinical information available were studied. Histologically characteristic ameloblastoma was found associated with this pattern in nine cases and one case, exhibiting only this pattern, recurred. It is concluded that the pattern in question is in fact ameloblastoma and that Vickers and Gorlin's criteria, although valuable, are too rigid for the diagnosis of this plexiform pattern of ameloblastoma in dentigerous cysts. There is need for further study on the natural behavior of these tumors. However, enucleation with good follow-up examination is probably sufficient for tumors that have proliferated into the cystic lumen, but more extensive surgery is indicated for those involving the periphery of the fibrous connective tissue wall of the cyst. This pattern occurs primarily during the second and third decades of life, generally in the mandible. The term "plexiform unicystic ameloblastoma" is proposed for this lesion to distinguish it from classical plexiform ameloblastoma.