X. Carcinoma of Mammary Gland Following Injection of Methylcholan-threne into Mice of NHO Strain

Abstract

Summary75 female mice of a total of 125 injected subcutaneously with 1 mg of methyl-cholanthrene at 60 days of age, developed carcinomas of the mammary gland. The mice belonged to the F14-F18 generations of inbreeding. This high incidence of mammary gland tumors was made possible by the suppression of local tumors through the process of genetic selection toward resistance to such local tumors. These induced mammary gland tumors duplicate the series of tumors produced spontaneously in genetic susceptible strains of mice such as the A and the C3H. In addition, however, the tumors arising in genetically resistant female mice of this experiment following the injection of methyl-cholanthrene possess 4 characteristics not present or less pronounced in the tumors of genetically susceptible female mice: (a) they show an increased tendency to undergo squamous metaplasia; (b) many of them (approximately 18%) undergo rather pronounced anaplastic changes, (c) these anaplastic tumors invade surrounding normal tissues ...