Benign Multicystic Peritoneal Mesothelioma Presents as a Tumor in an Elderly Man: An Uncommon Diagnosis

Background: Mesotheliomas are benign masses that can arise from any body parts that contain mesothelium, such as the abdominal, pelvic, pleural, and pericardial cavities. Benign multicystic peritoneal mesothelioma is a cystic tumor that arises from peritoneal mesothelial cells. It is a rare pathological entity, as only fewer than 200 cases have been reported. Benign multicystic peritoneal mesothelioma mainly occurs in women, and it is extremely rare in men. Its diagnosis and management are often challenging. Case presentation: This report demonstrates a case of a 61-year-old man who presented to the outpatient clinic with persistent abdominal discomfort that progressed over the years. He had visited different clinics and was referred to a gastroenterologist because of a misdiagnosis. After an extensive clinical evaluation, we failed to provide a definitive diagnosis; thus, diagnostic laparotomy for possible intra-abdominal malignancy was performed. After successful surgical resection of the lesions, the pathology was found compatible with benign multicystic peritoneal mesothelioma. Conclusion: Given its high recurrence rates and potential malignant transformation, meticulous and detailed surgical excision of the cystic lesions is of utmost importance to avoid repeated surgeries. Long-term follow-up is recommended.