Endometrial Metastasis from Breast Cancer during Adjuvant Endocrine Therapy

It is well-known that tamoxifen increases the risk of endometrial cancer. Although metastasis to the uterus from breast cancer is uncommon, there have been some case reports on uterine metastasis. If an endometrial abnormality is detected, the differential diagnosis of whether the uterine tumor is metastatic or primary is very important to determine the course of treatment. We herein report a case in which we detected a uterine tumor during follow-up after treatment with tamoxifen, and demonstrate that GCDFP-15 is useful in diagnosing metastatic uterine tumors arising from breast cancer.