[A Case of Breast Metastasis of Gastric Cancer after an Eight Year Latency Period].

A 66-year-old woman underwent distal gastrectomy because of gastric cancer(stage ⅠB)and received no adjuvant chemotherapy. Eight years after the operation, computed tomography showed a small nodule in the right breast. Mammography did not reveal any abnormalities. Ultrasound sonography showed a diffuse and gradual non-mass-like low echoic lesion. Core needle biopsy indicated a malignancy. Partial resection of the right breast was performed to obtain a diagnosis. On postoperative histopathological examination, signet-ring cells were found in the tumor, and immunohistochemical analysis showed that both the breast tumor and the gastric carcinoma were MUC5AC-positive and MUC1-negative. We diagnosed this breast tumor as metastasis from gastric cancer. The patient has received chemotherapy with no subsequent metastatic tumors, and good control has been achieved for 21 months after the detection of the breast metastasis.