[The ultrastructure of dyskeratotic and dysplastic keratinocytes in oral epithelium (author's transl)].

The fine structural morphology of dyskeratotic and dysplastic keratinocytes in human oral epithelium was investigated by light microscopy as well as by transmission and scanning-electron microscopy. On the epithelial-connective tissue border, marked changes are seen in the form of polymorphous microinvasive cytoplasmic processes of basal keratinocytes, structural alterations of the basement membrane and rarefaction of the subepithelial connective tissue. Dyskeratotic keratinocytes with abnormal tonofilament configuration are phagocytized by dermal macrophages and are transported to the lamina propria. Ultrastructural signs of atypia are found in the nucleus, nucleolus, cytoplasmic organelles and mitotic apparatus. Furthermore, multiple alterations of the plasma membrane, decrease in numbers of junctional complexes and acantholytic widened intercellular spaces are observed. Intracytoplasmic lumina are formed by endocytotic invagination of desmosome-studed plasma membrane regions at the cell surface. Despite an inverse relationship between the degree of keratinization and the glycogen content of the epithelium at the subcellular level, large amounts of glycogen are found in some keratinocytes. The epithelial surface is formed by hyper-, para-, or orthokeratosis, or shows individual cell keratinization, alteration of the disintegration process and defective keratin synthesis. The ultrastructural analysis of dysplastic keratinocyte populations reveals some morphological criteria common with invasive squamous cell carcinoma, which may be important in the early diagnosis and prognosis of malignant transformation of epithelial dysplasia.