Isolated Endometrial Metastasis of Invasive Ductal Carcinoma Simulating a Primary Uterine Malignancy: A Rare Case Report

Most common sites of metastasis from breast cancer are the lungs, bones, liver, and brain. Although metastasis to the uterus from breast cancer is uncommon, there have been some case reports on uterine metastasis. Among them, myometrium is involved more frequently comparing to endometrium. The majority of breast cancer metastases to endometrium are lobular type, and there have been only 7 reported cases of ductal type since 1984. In this study, a new case of invasive ductal carcinoma with metastases to endometrium and isolated presentation of abnormal uterine bleeding is described. 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. Atypical bleeding in patients with known breast carcinoma should prompt screening for endometrial metastasis by a gynecologist. Metastasis to the uterus carries a grim prognosis. 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.