BACKGROUND: Ameloblastoma is a benign odontogenic tumor, exhibiting local 
invasiveness and high rate of recurrence. Metallothionein is a protein 
associated with tumorigenesis, serving as prognostic factor in different 
neoplasms. We are interested in mechanisms underlying ameloblastoma local 
invasiveness. Thus, we decided to analyze expression of metallothionein in this 
tumor.
MATERIALS AND METHODS: An immunohistochemical evaluation of metallothionein in 
ameloblastoma was carried out. As control, we assessed expression of the same 
molecule in calcifying cystic odontogenic tumor (CCOT), a non-invasive 
odontogenic neoplasm with ameloblastomatous epithelium.
RESULTS: We studied 12 cases of solid/multicystic ameloblastomas. 
Metallothionein was observed in all samples. This molecule was observed in 
columnar cells in the periphery and in central polyhedral cells. CCOT (four 
cases) also showed the presence of metallothionein. Morphometry of stained areas 
showed that expression of metallothionein in ameloblastoma was significantly 
higher compared to CCOT (P < 0.0001).
CONCLUSIONS: This protein may have an impact on ameloblastoma behavior. 
Metallothionein would act as a zinc reservoir for important proteases related to 
ameloblastoma biology, such as MMPs. This protein could also display pro-mitotic 
and anti-apoptotic features in the tumor.