Susceptibility of Agent-Free Inbred Mice and Their F1 Hybrids to Estrogen-Induced Mammary Tumors

Abstract

Agent-free mice of inbred strains C3H, BALB/c, RIII, DBA/2, I, and C57BL and their reciprocal F₁ hybrids were tested for susceptibility to mammary tumors induced by the subcutaneous implantation of diethylstilbestrol-cholesterol pellets. Strain C3H mice, (BALB/c × C3H)F₁ hybrids, and (RIII × C3H)F₁ hybrids were the most susceptible to the hormone-induced tumors. The high incidence of tumors in these 3 groups of mice makes them suitable animals for use in experiments in which it is desirable to procure mammary tumors in the absence of the mammary-tumor agent. The morphologic types of the mammary tumors in mice of the present series were similar to those previously described. The histogenesis of the tumors in the present experiment, especially those in old male mice receiving large doses of estrogen, was different since the tumors usually arose within a focus of altered fibrocystic mammary tissue. A glioblastoma multiforme was found in one of the treated mice. No previous record of such a neoplasm has been found except in mice receiving chemical carcinogens intracerebrally.