A case of endometrial cancer developing during tamoxifen administration, coincidentally diagnosed as metastatic invasive lobular carcinoma of the breast to uterine serosa, ovaries, and pelvic lymph nodes

Abstract

Synopsis: It has been reported that gynecologic organ metastasis from breast cancer is comparatively rare. We report a case in which multiple pelvic metastases of breast cancer occurred simultaneously with endometrial cancer. The 47-year-old woman was referred to our department after initial treatment for invasive lobular carcinoma of the breast. An examination 15 months after starting tamoxifen revealed endometrial thickening on ultrasound, and adenocarcinoma on endometrial cytology. Histological examination by endometrial curettage identified endometrioid carcinoma, however, CT, MRI, and PET-CT led to no findings suggestive of malignancy. We performed total laparoscopic hysterectomy, bilateral salpingo-oophorectomy, and pelvic lymph node dissection for endometrial cancer. Pathological examination showed no cancer in the endometrium, but the metastasis of breast cancer to the uterine serosa, bilateral ovaries, and lymph nodes was noted. She was diagnosed with stage IA endometrial cancer and recurrent breast cancer. Invasive lobular carcinoma often metastasizes to the gynecologic organs and peritoneum, so we should pay close attention to the presence of peritoneal metastasis or metastasis to the uterus or ovaries during gynecological surgery in patients with a history of invasive lobular carcinoma, and if seeding or metastasis is suspected, changing the plan to biopsy or minimally invasive surgery to identify the primary tumor may be an option.Key words: endometrial cancer, metastatic breast cancer, invasive lobular carcinoma, tamoxifen