Effects of Estrogenic Hormones on the Mammary Tissue of Agent-Free and Agent-Bearing Male Mice2

Abstract

Three-week-old male (C3H × A)F₁ × C3H agent-bearing backcrossed hybrid mice were castrated and given injections of diethyl-stilbestrol thrice weekly. Agent-free (C3Hf × A_x)F₁ × C3Hf backcrossed hybrids from the same strains were similarly prepared and given injections of diethylstilbestrol or delestrogen. Mammary adenocarcinomas developed during the 7th to 11th months in 90 percent of the agent-bearing mice given injections. All the mammary glands were enlarged and filled with milk. The epithelial cells of the tumors and the nontumorous glands of the agent-bearing animals had budding B particles, and the intracellular spaces contained an abundance of mature B particles like those seen in female mice. None of the agent-free mice produced either a mammary tumor or B particles. These findings indicate that mice free of virus particles do not develop mammary tumors from steroid hormone treatment alone.