Abstract
In order to elucidate the characteristics of a hormonedependent mammary cancer, primary and serial transplantations of four mammary tumors induced by 7, 12-dimethylbenz (a) anthracene were carried out using inbred Fischer rats with different hormonal environments. Two primary tumors were successfully transplanted into the rats receiving estradiol or progesterone, showing strongly hormone responsiveness. The transplanted tumors regressed after withdrawing the hormone, and injection of estradiol and progesterone brought about a tumor regrowth after long period of dormant cells. The hormone responsiveness was lost by serial transplantation and metastasis occurred in rats with the hormone-independent tumor. The histologic appearance of the transplanted tumors was greatly altered by hormone, i.e., the tumor receiving estradiol showed plump epithelial cells with conspicuous vacuoles and large lumina of acini containing milk-like material, and the tumor receiving progesterone displayed fine acini composed of thin epithelial cells and the regressed tumor exhibited flattened epithelial cells, forming a single layer and outlining cystic spaces.
