Effects of exposure of neonatal mice to 17beta-estradiol on subsequent age-incidence and morphology of carcinogen-induced mammary dysplasia.

Mice exposed to estrogens as neonates developed more mammary dysplasias and had different morphologic types of dysplasias than did normal animals when both groups were exposed to a carcinogen: 1) before puberty, 2) during active mammary growth, 3) or at 6 months of age (the time when spontaneous dysplasias begin to appear in normal animals). The relative percentages of various morphologic types of dysplasias differed in hosts that received different treatments. The significance for subsequent patterns of mammary disease caused by exposure of neonates to 17beta-estradiol was discussed.