Peritoneal Benign Cystic Mesothelioma A 22 year old woman who has been followed for the diagnosis of FMF for the last five years was operated because of inguinal hernia in our hospital. A multicystic lesion, 4.5x3x1 cm in diameters, located in the inguinal area was found during the operation. There were cystic structures surrounded by mesothelial cells on the histopathologic examination. Benign cystic mesothelioma of the peritoeum is a rare entity and it was present because of its difficulty on the clinical and pathologic diagnosis.