Ascites as a Rare Manifestation of Malignant Peritoneal Mesothelioma: A Case Report

Malignant peritoneal mesothelioma (MPM) is an aggressive neoplasm that originates from the mesothelial cells lining the parietal peritoneum or visceral peritoneum and extensively spreads within the abdominal cavity. It is a rare malignancy characterized by an insidious onset and poor prognosis. We present the case of a 79-year-old Caucasian male who experienced escalating abdominal pain for six weeks and acute abdominal distension. His medical history was significant for hypertension, gastroesophageal reflux disease (GERD), hypercholesterolemia, and prior coronary artery bypass grafting (CABG). The patient had a 30-pack-year smoking history and worked as a plumber and roofer until retirement. We also confirmed with the patient that he has never been diagnosed with asbestosis. He reported no family history of mesothelioma or related conditions. A computed tomography (CT) scan revealed a prior sternotomy, mild pleural calcifications, mild hepatic steatosis, diffuse peritoneal ascites, diffuse omental edema, and pelvic phleboliths. MPM was confirmed through histopathological examination, which revealed atypical mesothelial cells with high nucleus-to-cytoplasm ratios, prominent nucleoli, and irregular nuclear membranes. It also revealed tumor cells positive for p53, calretinin, WT1, and podoplanin (D2-40). This case highlights the importance of considering MPM in the differential diagnosis for patients with ascites and possible asbestos exposure, particularly with respect to occupational hazards, as it is a rare manifestation of the disease.