Gastric Outlet Obstruction Caused by Metastatic Tumor of the Stomach Originating from Primary Breast Cancer: A Case Report

The most common sites of breast cancer metastasis are the bone, liver, lung and brain, while gastrointestinal metastasis from breast cancer is rare. We herein present the case of a 68-year-old woman who was admitted to our department with nausea and appetite loss. The patient's medical history included right mastectomy with sentinel lymph node biopsy 5 years earlier for invasive lobular carcinoma, measuring 6.2 cm in greatest diameter, without lymphovascular invasion. Two years after the surgery, the patient developed brain metastasis and underwent metastasectomy to control the neurological symptoms, including unsteadiness and asthenia. After the second surgery, the patient received systemic chemotherapy using S-1, followed by bevacizumab plus paclitaxel. However, due to bevacizumab-related cardiotoxicity, the treatment was switched to eribulin. On esophagogastroduodenoscopy, an elevated lesion was identified in the antrum, causing severe narrowing of the gastric outlet. Biopsy and histological examination of the tumor revealed infiltration of the gastric wall by undifferentiated neoplastic cells with poor adhesion, morphologically similar to invasive lobular carcinoma, and immunohistochemical staining was positive for estrogen receptor, mammaglobin and GATA3. Finally, 18F-2-deoxy-2-fluoro-D-glucose (FDG) positron emission tomography combined with computed tomography imaging revealed FDG uptake across the thickness of the antral wall. The patient was diagnosed with gastric metastasis from the original breast cancer and subsequently underwent endoscopic self-expandable metallic stent (SEMS) placement. There were no procedure-related adverse events, and the patient remained alive under best supportive care 4 months after SEMS placement. To the best of our knowledge, this is the first reported case of gastric outlet obstruction caused by metastatic breast carcinoma managed by SEMS placement. While such a diagnosis is rare, clinicians treating patients with gastric metastases should be aware of possible gastric outlet obstruction and SEMS placement as an effective palliative intervention.