Melanocytic carcinogenesis in albino guinea pigs.

We describe an experimental model for the induction of cutaneous melanomas in albino guinea pigs by means of repeated topical application of 7,12-dimethyl-benzanthracene over 13 consecutive months. At the end of the experiment 87.5% of the animals presented multiple lesions of a melanocytic nature. The most frequent and the earliest detected was melanocytic hyperplasia, followed by dysplasia. These lesions occurred in 75% of animals and were observed from the 4th month onward. Nevus-type lesions appeared from the 12th month and affected 70% of animals, whilst melanomas occurred in 65%. Metastases were observed in 45% of animals, in lungs, lymph nodes, kidney, and adrenal gland.