Dyskeratotic cells were examined with light and electron microscopy in human oral leukoplakias and carcinomas and in chemically-induced oral premalignant and malignant lesions of mice and rats. Specific antisera against small and large keratins were used to analyse the distribution of keratin polypeptides. In normal oral mucosa, basal cells did not react with antibodies against large keratins in contrast to the suprabasal cells which did react. Small keratins were found in all epithelial cell layers. In human and experimental premalignant and malignant lesions, intensely labelled dyskeratotic cells were seen, which contained small and large keratins regardless of their position in the epithelium. At the ultrastructural level, these cells showed dense aggregates of tonofilaments. Dyskeratotic cells were often seen in advanced stages of degeneration of phagocytosis of these cells by macrophages and giant cells was frequent. The disturbance of the keratinization process in oral precancer and cancer is easily visualized using keratin antisera. Keratin analysis can give new insights in epithelial maturation and may be helpful for the classification of oral leukoplakia.
