Tamoxifen exerts an estrogenic effect on vaginal and cervical squamous epithelium in post-menopausal women. This estrogenic effect may result in an increase in the maturation index on cytology.
A postmenopausal woman not receiving estrogen therapy should have a maturation index < 50 (if range 0 to 100; < 0.5 if range 0 to 1).
After several weeks of tamoxifen therapy the maturation index will be > 50 (Friedrich et al reported levels around 65) in women with low estrogen activity. This effect may not be so readily seen in women with a high estrogen activity (Shiota et al).
Women taking tamoxifen for a long period are at risk for developing endometrial hyperplasia and adenocarcinoma. These changes are more common if cytology shows:
(1) a high maturation index
(2) endometrial cells
Other drugs causing increased maturation:
(1) estrogen replacement therapy (avoided in women with a history of breast cancer)
(2) digitalis
(3) estrogenic compounds in herbal or alternative therapies
(4) topical estrogenic creams
Drugs causing decreased maturation:
(1) progestin therapy
(2) tetracyclines
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