Rationale: Breast cancer is a common malignant tumor. The most common metastatic sites of breast cancer are the bone, brain, liver and lung, and gastrointestinal metastases are rare. Considering that the median time interval from the initial breast cancer diagnosis to stomach metastasis is 77.5 months, gastrointestinal metastases are rarely observed 10 years after primary breast cancer.
Patient concerns: Here, we present a 63-year-old female with unusual endoscopy results that revealed scattered polyps and mucosal infiltration throughout the stomach, which were later confirmed to be metastatic lobular carcinoma of the breast that had been surgically removed 10 years earlier.
Diagnosis: The patient was diagnosed with gastric metastases of breast cancer by immunohistochemistry.
Interventions: The patient underwent endocrine therapy with palbociclib and tamoxifen.
Outcomes: After 1 year of endocrine therapy, the symptoms of upper abdominal discomfort and fatigue were relieved and a new gastroscopy revealed there had been no significant progression of the gastric metastasis. According to the Response Evaluation Criteria in Solid Tumors (RECIST), the patient reached a state of stable disease.
Lessons: Gastric metastases of breast cancer are rare in the clinical setting. However, considering the possibility of gastric metastases from breast cancer and performing an upper endoscopy are crucial for patients who present with any subtle gastric symptoms and have a past medical history of breast cancer, even if the breast cancer occurred more than 10 years ago.