Expression of tenascin and nucleolar organizer region in ameloblastoma and ameloblastic fibroma

The aim of this study was to assess the expression, distribution and comparison of tenascin, a glycoprotein of the extracellular matrix in ameloblastoma and ameloblastic fibroma, both odontogenic neoplasms with diverse biological behavior and to understand the proliferative activity by using the morphometric analysis.

Paraffin embedded tissue from 25 cases of odontogenic tumors i.e., ameloblastoma (n = 15) and ameloblastic fibroma (n = 10) were used. The expression of tenascin was evaluated using immunohistochemistry. Morphometric analysis of nucleolar organizer regions (NORs) from ameloblastoma and ameloblastic fibroma was carried out by silver staining.

A heterogeneous expression of tenascin was found in ameloblastoma which was mainly localized at the epithelial-mesenchymal interface and a patchy distribution was observed in the stroma (80%), while strong positivity was observed in the stroma and at the basement membrane zone of ameloblastic fibroma (100%). argyrophilic nucleolar organizer regions (AgNORs) revealed higher mean counts in ameloblastoma (3.093 +/- 0.902) when compared with those of ameloblastic fibroma (1.553 +/- 0.250). Ameloblastoma presented more than two NORs (two to five) per nucleus in majority of the cells, while ameloblastic fibroma exhibited only one NORs per nucleus.

Expression of tenascin in these neoplasms suggest that it could play a role in epithelial- mesenchymal interaction, while AgNORs reveal that ameloblastomas are more aggressive when compared with ameloblastic fibromas.