A Patient With Brain Metastasis From a Gastric Tumor.

Brain metastases secondary to gastric carcinoma are exceedingly rare and are associated with a poor prognosis. Their clinical presentation may mimic common neurological conditions, making early diagnosis and timely management challenging. We report the case of a 68-year-old male with a history of diabetes and hypertension who presented with sudden left-sided hemiparesis and urinary incontinence. Brain CT revealed a right frontal lesion with surrounding edema. He underwent craniotomy with tumor resection, and histopathological analysis confirmed a poorly differentiated gastric adenocarcinoma with human epidermal growth factor receptor 2 (HER2) overexpression (3+), consistent with brain metastasis of gastric origin. Systemic treatment with oxaliplatin and capecitabine was initiated, and anti-HER2-targeted therapy was considered. This report highlights the importance of maintaining a high index of suspicion for brain metastasis in patients with space-occupying lesions, even in the absence of a prior cancer diagnosis. The combination of neuroimaging, surgery, immunohistochemistry, and tailored oncologic treatment enabled timely intervention. The report underscores the value of interdisciplinary management and the clinical utility of biomarkers such as HER2 in guiding therapy in rare clinical scenarios.