[A study of epidermal alterations induced by PCDF on experimental carcinogenesis]

An effect of 2,3,4,7,8-pentachlorodibenzofuran (PCDF) as a promoter on a course of experimental skin carcinogenesis in mice by chemicals 20-methylcholanthrene (MC) has been proved by our previous studies. Details of ultrastructural epidermal alterations induced by MC and PCDF were observed and an attempt to differentiate benign tumor from malignant one in which a combined application of MC and PCDF on mice skin resulted was done electron microscopically. Four significant findings as follows were detected. First of all even the epidermal cells without tumor had some atypicality. Secondly both of benign tumor and normal-appeared skin without tumor had giant and round-shaped keratohyalin granules (KHGs) which show a tendency of less keratinization. Thirdly cytoplasmic projections of epidermal cells increased in number and sparse tonofilaments scattered in the cytoplasm of benign tumor. This is also an appearance of mucous metaplasia of keratinocytes as well as the form of KHGs mentioned above. Finally benign tumor had thick horny cells including numerous lipid droplets, and that is a sign of acceleration of epidermal turn over. Since epidermal cells have little chance to be exposed to carcinogens when they quickly keratinize, they rarely form a cancer. When epidermal cells have such tendency as less keratinization or more keratinization, they are supposed to be less sensitive to any stimuli of carcinogens, and consequently they incline to be benign tumor instead of malignant one.