[Benign cystic mesothelioma of the peritoneum]

A case of peritoneal cystic mesothelioma in a 40-yr-old woman is reported. The patient was operated on for signs of acute appendicitis. The lesion was made up of small, multiple, thin-walled cysts and both visceral and parietal layers of the peritoneum in the appendix region were involved. The lesion must be differentiated from other cystic lesions of the abdominal cavity and in particular from the multilocular lymphangioma. The diagnostic role of special techniques, such as immunohistochemistry and electron microscopy, in difficult cases is emphasized.