ELECTRON MICROSCOPIC STUDIES OF ORAL BENIGN LEUKOPLAKIA

1. 1. Electron microscopic studies of two cases of typical benign leukoplakia (oral hyperkeratosis) revealed that basal cells contain an abundance of thick, stranded tonofilaments and RNP particles. 2. 2. The squamous layer was thick, often comprising more than twenty cell layers. Squamous cells, unlike those in normal mucosa,1 were filled with abundant, thick tonofilaments which formed a heavily interwoven network in the cytoplasm. Other cellular organelles were compressed and masked by these tonofilaments. 3. 3. In the upper squamous layer and in the granular layer, RNP particles became aggregated in many foci in the cytoplasm and appeared to produce a dense material. As these aggregations enlarged, the dense material masked individual particles of RNP, and keratohyaline granules were formed. Even in large keratohyaline granules, RNP particles were still distinctly visible at their periphery. 4. 4. In spite of the presence of many layers of horny cells, the keratinization of these cells was still parakeratotic. Parakeratotic cells were characterized by the retention of nuclei, visible bundles of filaments, and the presence of lipid bodies. 5. 5. In the basal layor, melanocytes were actively producing melanin and transferring melanosomes to neighboring cells. Either Langerhans' cells or dense cells (which are similar to dermal histiocytes and Langerhans' cells except for Langerhans' granules) were very often found in the vicinity of the melanocytes. © 1968.