Nivolumab-induced tumour-like gastritis: A case report.

BACKGROUND: Immune checkpoint inhibitors are one of the modern treatment methods for advanced malignancies. However, this group of medications is also associated with various immune-related adverse events, such as colitis or pneumonitis. Immune checkpoint inhibitor-induced gastritis is a less common adverse event. CASE SUMMARY: We describe a 64-year-old woman presenting with diarrhea, nausea, and discomfort in the upper abdominal region. The patient had a history of metastatic lung cancer, which was treated with nivolumab. During the first endoscopy, an infiltrating gastric tumour was suspected. Later, based on endoscopic, histological and radiological findings, nivolumab-induced gastritis was diagnosed. The patient was successfully treated with three courses of omeprazole. CONCLUSION: As a consequence of the increased use of immune checkpoint inhibitors, a growing number of reported immune-related adverse events could be expected. The diagnosis of immune checkpoint inhibitor-induced gastritis should be considered when assessing a patient treated with nivolumab with upper gastrointestinal distress.