Radiologic manifestations of peritoneal mesothelioma

We report four cases of histologically proved peritoneal mesothelioma and describe the radiographic (mainly CT and angiographic) findings. There were three malignant diffuse tumors and one benign localized tumor. In one case, the lesion extended to the omentum and entrapped the fat tissue, and differentiation from peritonitis carcinomatosa was difficult. In the other three cases, reflecting necrotic change within the tumor, CT showed hypodensity throughout most of the mass. In two cases with hemorrhage, CT showed hyperdensity in the center of the mass. Angiography showed slight or medium neovascularity in the periphery of the tumor, but most of the tumor was avascular. Angiography was helpful for topographic diagnosis, but it was difficult to make a specific diagnosis or differentiate between malignant and benign types. We emphasize that it is important to consider peritoneal mesothelioma in the differential diagnosis when a mass of unknown origin is found in the abdomen, particularly when it is accompanied by necrosis and hemorrhage.