Calcifying epithelial odontogenic tumours in small domesticated carnivores: histological, immunohistochemical and...

Histological, immunohistochemical and electron microscopical studies revealed one feline and four canine calcifying epithelial odontogenic tumours in 115 oral tumours over a 10-year period. The tumours consisted of islands and sheets of odontogenic epithelium of varying size within a stroma of fibrous connective tissues. The tumour cells were pleomorphic with variable amounts of eosinophilic cytoplasm and large hyperchromatic, polymorphic nuclei with prominent nucleoli. Clusters of keratinized tumour cells ("shadow cells") were frequently seen within the islands and sheets. The multiple spherules of homogeneous eosinophilic material stained positively with Congo red and Dylon stains and produced an apple green birefringence under polarization microscopy, indicative of amyloid. Mineralized foci were scattered throughout the tumour masses and in the homogeneous spherules. Immunohistochemically, the tumour cells reacted with anti-human keratin antibody, but not with anti-human vimentin or anti-chicken desmin antibodies. The homogeneous spherules did not react with anti-human keratin, anti-human vimentin, anti-chicken desmin, anti-amyloid A, anti-laminin or anti-human collagen (type I, III, IV) antibodies. Ultrastructurally, the cytoplasm of tumour cells was abundant and contained a large number of electron-dense bundles of tonofilaments. The homogeneous spherules consisted of fine filaments measuring about 10-12 nm in diameter.