Background <p>Breast cancer is among the most commonly diagnosed malignancies worldwide. While distant metastases typically involve the bone, lung, liver, and brain, metastasis to the gastrointestinal tract is uncommon and occurs disproportionately in invasive lobular carcinoma (ILC). The clinical presentation is often nonspecific, which can delay diagnosis. This case presents the synchronous diagnosis of both primary breast cancer and gastric metastasis.</p> Case presentation <p>A 78-year-old woman presented with chronic belching, dyspepsia, and intermittent melena. Initial treatment and improvement with proton pump inhibitor therapy, suggested a primary gastrointestinal disorder. However, gastric biopsy confirmed metastatic invasive lobular carcinoma, and subsequent imaging revealed diffuse bony metastases.</p> Conclusions <p>This case highlights the synchronous diagnosis of gastric metastases originating from invasive lobular carcinoma with its associated diagnostic complexities and the limitations&#xa0;of traditional imaging modalities in detecting such metastases. Early recognition and accurate diagnosis are crucial for guiding appropriate treatment and improving patient outcomes. Therefore, we present a case that suggests considering breast cancer metastasis in the differential diagnosis for patients presenting with nonspecific gastrointestinal symptoms, even in the absence of breast-related complaints, is a reasonable clinical approach.</p>