Well-differentiated papillary mesothelioma is a rare mesothelial lesion with papillary architecture and bland cytology. It occurs slightly more commonly in the peritoneum than in the pleura. Peritoneal cases appear to be unrelated to asbestos exposure. The lesions are small, solitary, and usually discovered incidentally at laparotomy. Some consider them to be reactive lesions rather than true neoplasms. The involved peritoneal surface has a somewhat granular or velvety appearance resulting from multiple small nodules. The lesion shown here was found during resection of an ovarian cyst in a 29 y/o female. It consists of broad papillae covered by uniform cuboidal cells lacking atypia. Image copyright: pathorama.ch.