Peritoneal, benign, cystic mesothelioma with free-floating cysts, re-examined by new methods. A case report.

A histologically-confirmed, multicystic, benign mesothelioma, with free-floating, thin-walled cysts, in the abdominal cavity of a 27-year-old woman was reported in 1954. After removal of all visible cysts by laparotomy, the patient was healthy and well for 29 years, when she was surgically treated for cholecystitis and gall bladder stones in 1982. The whole peritoneum was found covered with small cysts lined by mesothelial cells. The patient is (April 1987) well, with no complaints. Sections from the old paraffin blocks were studied by means of scanning, transmission electron microscopy and immunohistochemistry. These methods confirmed the histological diagnosis. The authors discuss whether such a lesion really is a benign tumor or should rather be otherwise classified.