Keratoameloblastoma of the maxilla. A case report and review of the literature.

The keratoameloblastoma is a rare histologic variant of the ameloblastoma. Review of the English language literature revealed five case reports of keratoameloblastoma. We report the sixth case of this tumor. The tumor developed in the right posterior maxilla of a 26-year-old African-American man and demonstrated aggressive clinical behavior, analogous to conventional ameloblastoma. The initial biopsy specimen showed extensive cyst formation, which histologically resembled odontogenic keratocyst. However, the lining epithelium varied in thickness and there was separation and edema between the basal cells and the rest of the epithelium. The basal cells were strongly adherent to the underlying stroma unlike the basal layer of the odontogenic keratocyst, where cleavage often occurs in this area. Additionally, although the basal cells were palisaded and demonstrated nuclear polarization in areas, they were cuboidal rather than columnar. The excision specimen revealed more of a solid ameloblastic component in addition to the cystic component seen on the initial biopsy. Nevertheless, it is possible that the ameloblastoma had developed in an odontogenic keratocyst. Alternatively, it can be postulated that the keratoameloblastoma consists of both cystic and solid components, the former being analogous to the cysts of the conventional ameloblastoma.