Abstract
BACKGROUND: Metastatic breast cancer originating in the gastrointestinal tract is a rare occurrence. The limited number of cases has resulted in incomplete understanding of the disease, making it challenging to differentiate from primary breast cancer. While clinical history and immunohistochemical studies can aid in distinguishing between the two, the management principles and pathogenesis of gastrointestinal metastatic breast cancer remain controversial. The scarcity of data has hampered comprehensive knowledge. Our objective is to shed light on this rare disease through our case study. CASE SUMMARY: Here, we report a case of breast metastasis from gastric cancer in a 43-year-old woman. This patient was admitted to our hospital with complaints of discomfort in the upper and middle abdomen persisting for two months, as well as black stools for over ten days. She underwent radical distal gastrectomy for gastric cancer, followed by postoperative chemotherapy. Three years later, the patient developed bilateral breast nodules. Imaging studies indicated a high probability of malignancy. She subsequently underwent a right modified radical mastectomy and excision of a left breast mass. Postoperative pathology revealed the right breast tumor was consistent with primary gastric cancer. CONCLUSION: We present a case of breast metastasis from gastric cancer to contribute to the limited foundation of research into this rare disease.