Risk of malignant mixed mullerian tumors after tamoxifen therapy for breast cancer

Recent studies have indicated that the tamoxifen-related risk of uterine cor-pus cancer may be especially high for some uncommon cell types, although the magnitude of risk has not been quantified. We evaluated data from 39 451 breast cancer patients diag-nosed from 1980 through 2000 who were initially treated with tamoxifen and found that the overall risk of sub-sequent uterine corpus cancer was in-creased more than twofold (observed-to-expected ratio [O/E] 2.17, 95% confidence interval [CI] 1.95 to 2.41) relative to the general SEE