Histological and ultrastructural observations of eosinophilic keratohyalin granules in filiform papillae of pig tongue.

Cells in filiform papillae of pig tongue possess distinct granules that stain with eosin but little or none with hematoxylin. This eosinophilia differs from the classically described basophilia of keratohyalin granules as is described in skin and keratinized oral mucosa of many species. At the ultrastructural level, electron-dense granules were observed in the cytoplasm and occasionally in the nuclei of cells within the papillae. The granules were round, oval or irregular in shape and varied in size and density. The ultrastructural characterization of these eosinophilic granules is the first reported in the literature.