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.

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.

We present a case of breast metastasis from gastric cancer to contribute to the limited foundation of research into this rare disease.

Although gastric cancer is known to be an aggressive tumor that can spread throughout the body, breast metastases are uncommon. This entity is rarely reported in the literature, with an estimated incidence of 0.5 to 1.3%. We report a case of a rare association between a gastric subtype of signet ring cell carcinoma and metastasis to the breast. This uncommon situation is only documented through case reports. Most breast metastases have been detected after diagnosis of primary gastric cancer, during the first year. Several risk factors have been suggested to explain the aggressive behavior of these tumors, which correlates with very poor prognosis and short survival. We report the case of a 22-year-old female patient presenting with widespread metastatic gastric signet ring cell carcinoma with an unusual secondary site in the breast. The diagnosis was confirmed by immunohistochemistry (IHC) and radiology, and the patient was treated with palliative chemotherapy in accordance with the decision of the multidisciplinary tumor board.