Malignant mixed mesodermal tumor after tamoxifen therapy for breast cancer

The risk of tamoxifen related endometrial neoplasm has been confirmed by multiple studies. Especially rare endometrial tumors seem to develop more frequently under tamoxifen therapy. A recent analysis showed a substantially higher risk for malignant mixed mesodermal tumor (MMMT; designated in the WHO classification of female genital tract neoplasms as carcinosarcoma) in association with tamoxifen intake.

We are reporting a case of a 40-year-old multiparous premenopausal woman who received tamoxifen 20 mg daily for 2 years after the surgical treatment of breast cancer and subsequent adjuvant chemotherapy. Two years after initiation of tamoxifen treatment, the patient developed an MMMT of the uterus. More than 64 months after radical hysterectomy, salpingo-oophorectomy, and pelvic lymphadenectomy, she remains recurrence-free for MMMT. Unfortunately, she developed a local recurrence of her breast cancer in 2003. After surgical treatment, she is currently being treated with anastrozole.

We are reporting a rare case of a premenopausal patient who developed a MMMT within short time of tamoxifen exposure for stage I breast cancer.