Cystic mesothelioma of the peritoneum.

Cystic mesothelioma (CM) of the peritoneum is a rare, benign neoplasm that occurs predominantly in women and tends to recur locally. It has received little attention (to our knowledge, a single case report) in the radiology literature. Five cases of CM are presented. Computed tomography (CT) was performed in three cases, ultrasound (US) in four cases, and magnetic resonance (MR) imaging in one case. Twenty-eight cases reported in the literature are reviewed for comparison. CM shows a clear predilection for the surfaces of the pelvic viscera but is seen in other areas of the peritoneum and retroperitoneum. The neoplasm was intraperitoneal in three cases and primarily retroperitoneal in the other two cases. In all CT and US studies performed, a single large, multilocular cystic mass was demonstrated. MR imaging, performed in one case, showed that the lesion had signal characteristics typical of a watery collection low in solute concentration. It is concluded that CM of the peritoneum has a nonspecific multilocular cystic appearance on images, which does not permit it to be differentiated from other cystic lesions.