Adenomatoid odontogenic tumour: immunohistochemical demonstration of transferrin, ferritin and alpha-one-antitrypsin.

Three cases of adenomatoid odontogenic tumour (AOT) were examined by morphological and immunohistochemical methods, to define the nature of tumour cells and to determine the correlation between the occurrence of extracellular eosinophilic amorphous material and epithelial tumour cells. The epithelial tumour cell components observed in this study were divided into three cell types (cell type I: small compact cells in a solid nodule and pseudoglandular cells in a duct-like structure; cell type II: peripheral elongated cells and spindle-shaped cells in a cribriform pattern; and cell type III: metaplastic squamous cells). The mesenchymal components consisted of eosinophilic amorphous material and calcified material. Immunohistochemically, the type I cells reacted positively with antibodies to transferrin, ferritin and alpha-one-antitrypsin (alpha1-AT), whereas the type II cells constantly indicated intense expression only for transferrin and alpha1-AT. All types of epithelial tumour cells reacted negatively with lactoferrin, alpha-one-antichymotrypsin, S-100 protein, S-100alpha subunit and S-100beta subunit. Moreover, the eosinophilic amorphous material and calcified material examined were positive for the antibody against alpha1-AT. These materials expressed immunophenotypes similar to those of the epithelial tumour cells, except for metaplastic squamous cells. The present study showed that iron-binding proteins and proteinase inhibitor might be related to the pathogenesis of AOT. Furthermore, we indicated that the formation of eosinophilic amorphous material was associated with type I and type II cells.