In vitro influence of estradiol or progesterone on the thymidine labeling indices of human benign breast tumors.

Using an in vitro tritiated thymidine (3H-dThd) nuclear labeling followed by autoradiography, the effects of 17-beta-estradiol (E2) or progesterone (Pg) on cell proliferation were studied in 22 human benign breast tumors, i.e. 7 fibroadenomas 8 fibrocystic dysplasias 4 gynecomastias and 3 phyllodas.