Uterine metastasis of lobular breast carcinoma under tamoxifen therapy: A case report.

Uterine metastases from breast cancer are uncommon and have rarely been reported in the previous literature. The present report describes the case of a 66-year-old female who developed uterine metastasis 23 years following the primary treatment of invasive breast cancer. Specifically, the patient experienced multiple bone metastases 14 years following primary treatment and had previously been treated with aromatase inhibitors followed by tamoxifen citrate. The patient presented with abnormal genital bleeding and was referred to the Gynecology Department of the Osaka City University Hospital (Osaka, Japan) 23 years following the primary treatment. The results of an endometrial biopsy revealed adenocarcinoma. Initially, it was difficult to differentiate between primary endometrial adenocarcinoma and metastatic adenocarcinoma from breast cancer. The results of pelvic magnetic resonance imaging demonstrated uterine myometrium enlargement and no endometrial thickness. Furthermore, an abdominal total hysterectomy, bilateral salpingo-oophorectomy and a biopsy of the peritoneum were performed. The pathological examination of the resected uterus revealed adenocarcinoma, which proliferated diffusively in the cervical stroma, myometrium, cardinal ligament, bilateral adnexa, omentum and peritoneum. Immunohistochemical results revealed the positive staining of gross cystic disease fluid protein-15, as well as negative staining for CD10 and E-cadherin. Thus, the tumor was diagnosed as metastatic adenocarcinoma from the breast lobular carcinoma. The patient has since been treated with fulvestrant, toremifene citrate and tegafur, and the current patient survival duration is 2 years and 8 months. In conclusion, when patients with breast cancer undergoing hormonal therapy, such as tamoxifen, present with abnormal genital bleeding, future diagnoses should consider both endometrial cancer and uterine metastasis from breast cancer.