Skin carcinogenesis as a model system: observations on species, strain and tissue sensitivity to 7,12-dimethylbenz(a)anthracene with or without promotion from croton oil.

The pattern of development of tumours was studied in several mice strains, rabbits and pigs. Repeated carcinogen applications caused the appearance of numerous papillomas, keratoacanthomas and squamous cell carcinomas in Swiss, A, ASW/SN Balb/c and C57B1 mice, New Zealand and outbred laboratory rabbits. AKR mice were only little sensitive and Hormel mini pigs unresponsive. Initiation with 7,12-dimethylbenz(a)-anthracene and promotion with croton oil produced in Swiss, A, Balb/c and C3H mice as well as New Zealand rabbits a large number of squamous papillomas. Pigmented or adnexal tumours were not observed, and only a few dermal fibromas and fibrosarcomas.