Isolated breast metastasis from gastric cancer in a male patient.

A 72-year-old man underwent total gastrectomy for gastric cancer (por2, T3, N2, Stage IIIA). Eleven courses of postoperative chemotherapy with TS-1 (tegafur/gimeracil/oteracil) were administered. Five months after surgery, the serum carcinoembryonic antigen value was slightly elevated. However, computed tomography did not reveal any metastatic lesions in other organs. Two years after surgery, the patient felt a mass in the left mammary. A 2-cm tumor was palpable in the central portion of the breast. Ultrasonography revealed a hypoechoic tumor, which was Class 3 on aspiration biopsy cytological examination. No mass was detected on positron emission tomography-computed tomography. The mammary gland tumor increased in size to 3 cm, and a core needle biopsy procedure was performed. Histological examination findings revealed breast metastasis of gastric cancer. No other recurrence was found, and radical mastectomy was performed 2 years and 5 months after gastrectomy. Immunohistological analysis of the resected material confirmed breast metastasis of the gastric cancer. Two courses of TS-1 + cisplatin were administered, but this treatment was subsequently terminated because the patient experienced Grade 3 diarrhea and neutropenia. Three years and 1 month after the gastrectomy, the tumor recurred in the pelvic area. Chemotherapy and radiation therapy were performed, but the patient's overall condition became progressively worse, and he died 3 years and 9 months after gastrectomy.