Adenomyomatous polyp of the uterus in a patient receiving tamoxifen.

We report a case of adenomyomatous polyp that developed during treatment with tamoxifen for breast cancer. A 63-year-old Japanese woman was admitted complaining of atypical genital bleeding. Nine months earlier, she had undergone a modified radical mastectomy for cancer of her right breast, estrogen receptor-positive stage I (T1N0M0). The administration of tamoxifen, 20 mg/day, was started immediately postoperatively. Pelvic examination after tamoxifen administration for 9 months revealed that the uterus was enlarged to the size of a fist. Transvaginal ultrasonography and magnetic resonance imaging revealed a large solid mass with multiple cystic areas in the uterine cavity. The pathological diagnosis of the tumor after total hysterectomy was typical adenomyomatous polyp. It was believed to have developed during tamoxifen administration.