Odontogenic Gingival Epithelial Hamartoma; with Reference to the Expression of Ameloblastin Gene by in situ Hybridization and Immunohistochemistry

ABSTRACT

Odontogenic gingival epithelial hamartoma (OGEH) is an extremely rare lesion characterized by an abnormal proliferation of odontogenic epithelium. This lesion is thought to arise from the rest of the dental lamina lying dormant in the gingival tissue after odontogenesis. Distinguishing OGEH from the granular cell variant of ameloblastoma and central odontogenic fibroma is important. To date, only eleven cases have been reported, and its pathogenesis remains unclear. We report here on a case of OGEH, where the epithelial strands in the lesion were conspicuously positive for the antisera of cytokeratin 19 and ameloblastin. Tumor cells intensely expressed ameloblastin mRNA by in situ hybridization. To the best of our knowledge, this is the first case of OGEH to which ameloblastin immunohistochemical stain and in situ hybridization were applied. Although our study is limited to a single case, the coexpression of cytokeratin 19 and ameloblastin might indicate the origin and specific cytodifferentiation of OGEH is quite different and unique, when contrasted to other odontogenic tumors.