This work was undertaken to determine if the ultrastructural changes seen in mouse skin carcinogenesis ( Tarin, 1967a) are specific to the carcinogenic process.
Electron microscopic examination of skin treated with non-carcinogenic irritant chemicals (benzene, turpentine) showed that the dermo-epidermal junction remained intact. The changes seen in this region in methylcholanthrene-treated skin were not present.
The irritants did, however, produce changes in the epidermis and dermis but these differed from those seen in carcinogen-treated skin. The epidermis underwent regular hyperplasia and there was an increase in the number of inflammatory cells in the dermis. Dermal collagen fibre structure and arrangement were not altered.
It is concluded that the changes seen at the dermo-epidermal junction in carcinogentreated skin are directly related to the carcinogenic process and are not the result of non-specific irritation.
The nature of the carcinogenic process is considered and disturbance of interaction between epithelium and connective tissue is offered as an explanation for the behaviour of neoplastic tissue. This hypothesis is discussed in the context of modern work which has shown that such interactions are of importance in the development and maintenance of normal tissue architecture.