Cytoreductive surgery and HIPEC for multicystic peritoneal mesothelioma: therapeutic approach in a rare benign neoplasm.

Multicystic peritoneal mesothelioma (MCPM) is an uncommon tumor of mesothelial origin, characterized by multiple interconnected cystic spaces and uncertain biological behavior. Although traditionally considered benign, its tendency to recur and occasionally spread within the peritoneal cavity challenges this perception. We describe a 32-year-old woman who experienced gradually worsening pelvic pain and a constant feeling of pressure, which intensified after childbirth. Imaging revealed a large multilocular cystic mass occupying the pelvis. At laparotomy, a gelatinous, multilocular lesion was found adherent to the pelvic peritoneum, uterus, ovaries, and rectosigmoid colon. Complete cytoreductive surgery was performed, including pelvic peritonectomy, omentectomy, appendectomy, and resection of the affected serosa, followed by closed-abdomen hyperthermic intraperitoneal chemotherapy (HIPEC) with oxaliplatin (300 mg/m2, 42°C, 90 min). Histopathology confirmed benign multicystic mesothelioma with a mesothelial immunophenotype. The patient recovered well and remains disease-free at 6 months. MCPM requires complete cytoreduction, and HIPEC may help achieve lasting disease control.