Mammary carcinogenesis in (C3H X RIII) F1 mice under different experimental conditions.

In (C3H X RIII) F1 females a disturbed hormonal balance plays the major role for the etiology of mammary carcinomas. Castration early in life delays the appearance of the tumors. In normal females the adrenal secretions do not intervene in carcinogenesis. In forced bred females or in animals with pseudopregnancies, but not in mothers which nursed their offspring the latencies are shortened. After a graft with one male pituitary to a castrated female the latency is the same as in intact animals. Pituitary grafting to castrated males does not change the frequency or the latencies of spontaneous mammary cancers. One mammary cancer was observed in an intact male implanted with a pituitary. It is stated that in our animal model progesterone is not an essential factor for mammary carcinogenesis.