A Case of Synchronous Metastasis of Breast Cancer to Stomach and Colon

A case of synchronous metastasis of breast cancer to the stomach and colon is reported. A 38-year-old woman with a history of bilateral breast cancer was admitted for endoscopic examination because of occult blood. Endoscopic examination showed elevated lesions on the mucosal surface of the stomach and cecum. Histopathological examination of the biopsy specimens obtained from both sites showed adenocarcinoma, comprised of tumor cells with structural and nuclear atypia, which were similar to those of the primary breast cancer cells. In immunohistochemical analysis, these tumor cells stained positive for ER. Therefore, we diagnosed a synchronous metastasis of breast cancer to the stomach and colon. Synchronous metastasis of breast cancer to the stomach and colon without liver metastasis or peritoneal dissemination is extremely rare, with only 4 reported cases existing in literature. Breast cancer is the most common malignancy among women in Japan and in Western countries. The life-time risk for development of breast cancer in women is 5% (1). Common sites of breast cancer metastases include the lungs, liver, bones, and soft tissues. Metastatic disease in the gastrointestinal (GI) tract has been rarely reported (2). Borst and Ingold reported metastasis of breast cancer to the GI tract (MBGI) in only 17 of 2,604 cases (less than 1%) over an 18-year period (3). Other studies on MBGI are limited to autopsy cases (4, 5); thus, information on MBGI is scarce. We present a case of synchronous metastasis of breast cancer to the stomach and colon and discuss the clinicopathological characteristics of MBGI along with a review of the literature. Case Report A 38-year-old woman whose stool sample tested positive for occult blood during a medical check-up was admitted to the hospital for endoscopic examination. Three years ago, she had undergone left modified-mastectomy with axillary dissection for the treatment of lobular carcinoma (T2N1M0). Immunohistochemical analysis of the invasive lobular carcinoma after surgery (Figure 1) revealed positive staining for estrogen receptor (ER), but negative staining for progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER2). The patient was sequentially administered four courses of epirubicin/cyclophosphamide (EC) therapy with 90 mg/m 2 epirubicin, 600 mg/m 2 cyclophosphamide, and 80 mg/m 2 paclitaxel. She also underwent radiation therapy to the chest wall and supraclavicular fossa, along with tamoxifen (20 mg/day) and luteinizing hormone-releasing hormone agonist (3.6 mg/month). One year ago, she underwent right partial-mastectomy with sentinel lymph node biopsy for the treatment of lobular carcinoma (T1N0M0, ER+, PR-, HER2-), followed by four courses of docetaxel (70 mg/m 2 ), and radiation therapy to the