Epidermal-dermal junction during experimental skin carcinogenesis and cocarcinogenesis as revealed by scanning electron microscopy.

During epidermal carcinogenesis important changes in the epidermal-dermal junction take place. Because of methodological difficulties may be these changes, especially those concerned with three-dimensional organization of the junction, remain unsatisfactorily investigated. To obtain new information, we studied with scanning electron microscopy (SEM) the development of carcinogenic changes in the epidermis of mice induced by DMBA-TPA, DMBA alone, and by the cocarcinogen TPA alone. We correlated the results with those from transmission electron microscopy and light microscopy. Although the epidermal changes morphologically showed similarities, biologically they differed. With them, distinct changes in the epidermal-dermal junction developed, that could be followed through early, hyperplastic and neoplastic phases. With the SEM the first changes were seen in the basal layer of the epidermis and concerned the cell arrangement. SEM provided information about the localization and development of incipient epidermal carcinomas induced by DMBA-TPA and DMBA treatment, as well as about the changes in the basal lamina. These can be classified by their surface, their extent and their frequency throughout large regions. Our studies indicate that these changes vary greatly, depending upon the treatment used and the time of their development. Only the progressive disintegration of the basal lamina is characteristic of carcinogenesis.