<p>Menstruation is suppressed in a proportion of premenopausal women receiving Tamoxifen for the treatment of breast cancer. An increased incidence of endometrial cancer has seen reported in association with Tamoxifen treatment. The underlying mechanism is unknown, but may be related to the oestrogen-like effect of Tamoxifen. Any patients receiving or having previously received Tamoxifen, who report abnormal gynaecological symptoms, especially vaginal bleeding, should be promptly investigated.<br />
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A number of second primary tumors, occurring at sites other than the endometrium and the opposite breast, have been reported in clinical trials, following the treatment of breast cancer patients with Tamoxifen. No causal link has been established and the clinical significance of these observations remains unclear.</p>