[A Case of Gastric Metastasis from Breast Cancer Detected 12 Years after Surgery].

Gastric metastasis of breast cancer is clinically rare and its diagnosis is often delayed because of the difficulty in differentiating it from primary gastric cancer. Here, we report a case of gastric metastasis identified 12 years after surgery for left-sided breast cancer. Gastrointestinal symptoms prompted an upper gastrointestinal endoscopy, which revealed an elevated gastric lesion. Immunohistochemical staining of the lesion showed positivity for CK7, GATA-3, mammaglobin, and GCDFP-15, and negativity for CK20, leading to the diagnosis of gastric metastasis from breast cancer. When gastrointestinal symptoms occur in patients with a history of breast cancer, it is important to consider gastric metastasis in the differential diagnosis and perform a thorough evaluation, including immunohistochemical analysis.