Unusual ameloblastoma with extensive stromal desmoplasia.

A clinicopathological study of 5 cases of unusual ameloblastoma was performed. Three cases were characterized by marked stromal desmoplasia. The lesions occurred in the tooth-bearing areas of the anterior or premolar regions of the jaw. They were relatively small and showed a honeycomb appearance radiographically. Histologically, the islands of tumour cells were small and discrete in the widely extended desmoplastic stroma. They lacked obvious ameloblastic polarity in many parts. The other 2 cases were hybrid lesions of desmoplastic and conventional types. The former appeared in the alveolar part and the latter in the lower part of the mandible. It was concluded that the desmoplastic variant of ameloblastoma could be categorized as a new distinct type histologically, clinically and radiographically.