‘Hybrid’ desmoplastic ameloblastoma: an unusual case report with immunohistochemical investigation for TGF-ß and review of literature

Ameloblastoma, a relatively common epithelial odontogenic tumor includes several histopathologic subtypes like follicular, plexiform, acanthomatous and desmoplastic variants. Hybrid desmoplastic ameloblastoma (DA) composed of typical desmoplastic ameloblastoma along with areas of follicular/plexiform ameloblastoma is an extremely rare variant of ameloblastoma and to date only 16 cases have been documented. We report a new case of hybrid DA which additionally showed remarkable histologic findings of extensive bone formation and presence of mucous cells. It occurred in a 64 year old female patient involving the left maxilla from lateral incisor to distal to first molar. A comprehensive review of hybrid DA and the unusual findings aimed to offer an insight into the pathogenesis of these heterogeneities in odontogenic epithelium and clinical implications was also undertaken. Hybrid DA showed characteristic clinicopathologic features of a desmoplastic ameloblastoma with the exception of predominant mandibular occurrence. A likelihood of areas of solid multicystic ameloblastoma being a part of histopathologic spectrum of DA questioning the need for use of term “hybrid” was observed. Regarding the osteoplasia, most cases occurred in Asians and in anterior maxilla. The prominent TGF-ß expression seen in our case adds emphasis to its role in desmoplasia and osteoplasia. Furthermore, we identified an interesting association of desmoplasia with incidence of mucous cell metaplasia in ameloblastoma.