Reproductive tract abnormalities in female mice treated neonatally with tamoxifen.

Immature female mice of the NMRI strain were treated with 20 micrograms/day of tamoxifen or vehicle for the first 3 days after birth. At 90 days of age, vaginas, uteri, and ovaries were examined histologically. A benign epithelial change, vaginal adenosis characterized by abnormal growth of columnar epithelium with glandular structures, was found in all of the tamoxifen-treated mice. Anatomic anomalies such as hypospadias, cervical hypoplasia, uterine hypoplasia, and absence of corpora lutea also were commonly observed. Such abnormalities were not found in the control mice.