Evaluation of Amelotin Expression in Benign Odontogenic Tumors

Abstract

Objective: Amelotin (AMTN) is highly and selectively expressed by odontogenic epithelium-derived ameloblasts throughout the maturation stage of enamel formation. The protein is secreted and concentrated at the basal lamina interface between ameloblasts and the mineralized enamel matrix. Odontogenic tumors (OT) are characterized by morphological resemblance to the developing tooth germ. OT vary from slowly expanding, encapsulated tumors to locally aggressive and destructive lesions. The purpose of this study was to determine the expression profile of AMTN in benign odontogenic tumors and to correlate it with specific features of the lesions. Methods: Immunohistochemical staining for AMTN was performed on human ameloblastoma, ameloblastic fibroma (AF), ameloblastic fibro-odontoma (AFO), odontoma, adenomatoid odontogenic tumor (AOT) and calcifying cystic odontogenic tumor (CCOT). Results: Generally, ameloblastoma and AF did not stain for AMTN. A strong signal was detected in ameloblast-like layers of AFO and odontoma. Epithelial cells in AOT did not stain for AMTN, while calcifying areas of extracellular eosinophilic matrix were intensely stained. Interestingly, ghost cells present in odontomas and CCOT revealed variable staining, again in association with calcification foci. Conclusions: Amelotin expression was consistently detected in tumors presenting differentiated ameloblasts and obvious matrix deposition. Additionally, the presence of the protein in the eosinophilic matrix and small mineralized foci of AOT and calcification areas of ghost cells may suggest a role for AMTN in the control of mineralization events.