Abstract
Summary
1. Hormone dependence of original (spontaneous, radiation- and 3-methyl-cholanthrene induced) mammary tumors were compared with first and second generation grafts of the same tumor in fully histocompatible inbred strains of rats. 2. Almost all tumors, (carcinomas and fibroadenomas) were autonomous in that they grew in normal hosts of both sexes, but most of them were hormone responsive. 3. A fair index of responsiveness is the degree of preferential growth of tumors in females. 4. Growth is retarded by ovariectomy and hypophysectomy and is resumed upon subsequent grafts of mammotropic tumors (administered to supply mammary gland stimulating hormones). 5. Progression appears invariable in the course of transplantations in the strains studied, but hormonal responsiveness in the first passages was almost identical with that of primary tumors. 6. Malignancy, hormone responsiveness, and growth rate vary independently. A slow growing fibroadenoma can be hormone independent and rapidly growing, while a carcinoma can be highly hormone responsive. These experiments support the hypothesis which considers the mammotrope of the pituitary and its hormones to be the main direct stimulant of the mammary gland and its tumors.
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