Pembrolizumab related perforated appendicitis.

Introduction: Pembrolizumab is a humanized monoclonal antibody IgG4 programmed cell death protein 1 antagonist, and its use in oncology has been increasing in recent years, providing durable and favorable responses and tolerable toxicity profiles in various types of cancer. We describe a case of pembrolizumab related perforated appendicitis in a patient with stage 3C malignant melanoma (MM).

Case report: A 70-year-old male patient who had no known disease was diagnosed with MM as a result of the excision of the mass on his right shoulder. The disease stage was stage 3C (pT4aN1bM0). Subsequently, adjuvant pembrolizumab treatment was started. A few days after the fourth maintenance course, he presented to the emergency department complaining of abdominal pain, nausea and vomiting. Emergency abdominal tomography showed a significant increase in the diameter of the appendix vermiformis, peritoneal thickening and appendiceal wall defects that could be significant in terms of perforation.

Management and outcome: The mentioned finding and given the clinical presentation, was attributed to a perporating of the appendix, so the patient was hospitalized in the Department of Surgery and the patient underwent emergency appendectomy. Histological findings were consistent with appendicitis. After a day in the hospital, the abdominal pain subsided, C-reactive protein tended to decrease and the patient was discharged.

Discussion: In patients who develop acute abdominal pain with or without diarrhea during immunotherapy, urgent imaging, endoscopic and clinical evaluation should be performed, and bowel perforation, although rare, should be considered as a potential complication of any immunotherapy.