Abstract
Mesothelioma is a rare neoplasm with a minority of cases originating from the peritoneum. Patients are generally treated with a combination of cytoreductive surgery, hyperthermic intraperitoneal chemotherapy, and various systemic therapies. In recent years, expression of programmed death ligand 1 (PD-L1) has been investigated in mesothelioma with implications for targeted therapy. In this case report, we present a patient with solitary isolated peritoneal mesothelioma of the right flank with abdominal and chest wall involvement and high PD-L1 positivity. The patient demonstrated a remarkable metabolic response to neoadjuvant immunotherapy using nivolumab and ipilimumab, which was followed by a successful surgical resection. Pathological evaluation revealed a complete pathological response, highlighting the effectiveness of the treatment strategy.