Oestrogen-like effect of tamoxifen on vaginal epithelium.

30-40 mg tamoxifen were administered orally in 86 postmenopausal women with late breast malignancy who were found to be resistant to standard endocrine and chemotherapy 2 months previous to this treatment. Vaginal smears were taken before and after 30-45 days treatment. A zero pyknotic index was seen before treatment. After tamoxifen, the index regularly increased to values between 10-30% reaching 50% in 4 cases and 80% in 1. Smears became atrophic within 2 months of withdrawal of treatment. 32% of the patients responded, showing an objective tumor regression. It is unclear whether the tumor is reacting to tamoxifen as if it were an estrogen.