The amyloid deposit in calcifying epithelial odontogenic tumor is immunoreactive for cytokeratins

Calcifying epithelial odontogenic tumor, also known as Pindborg tumor, is a rare benign tumor with locally aggressive behavior. It is characterized by squamous epithelial cells, calcifications, and eosinophilic deposits that have been identified as amyloid. We report a case of calcifying epithelial odontogenic tumor and investigate the nature of the amyloid, using histolog ic, immunohistochemical, and ultrastructural studies. The amyloid was immun ohistochemically negative for basement membrane components and positive for all cytokeratin stains performed (cocktail of cytokeratins 1, 5, 6, 8, 13, and 16, and cytokeratins AE1 and AE3). The amyloid stained focally in a gl andular-like pattern, reminiscent of the epithelial glandlike structures of the tumor. We conclude that the amyloid is derived from filamentous degene ration of keratin filaments that originate from the tumor squamous epitheli um. The keratin degeneration is part of a developmental or aging process th at the tumor undergoes.