Neoplasms in domestic animals: a review of experimental and spontaneous carcinogenesis.

Clues to environmental and host factors in human oncogenesis are derived from clinical or epidemiologic studies; additional evidence is provided by animal experimentation. Induced tumors in animals are useful because of their reproducibility and predictability, allowing detailed study of specific carcinogens or carcinogenic influences. Spontaneously or naturally occurring tumors in domestic animals are of particular interest for comparative studies - these tumors occur in heterogenous outbred populations of animal closely sharing man's environment; their cause is generally unknown; many tumors occur in numbers suitable for detailed investigations; and tumors generally occur in aged animals, thus facilitating study of chronic processes associated with carcinogenesis in nature.