Report of a case of benign cystic mesothelioma.

A 32-yr-old man was admitted to Anjo Kosei Hospital for the examination of a cystic peritoneal lesion. This patient had a past medical history significant for an appendectomy. Ultrasonography and computed tomography revealed multiple cysts in the abdominal and pelvic cavities. An exploratory laparotomy was performed on July 1, 1993, revealing numerous thin-walled and translucent cysts in the serosal tissues of the parietal and visceral abdominal peritoneum. These cysts were excised surgically because of clinical suspicion of pseudo-myxoma peritonei. Microscopic examination revealed cysts within the thin cyst wall that were composed of fibrous connective tissue and lined by a single layer of cuboidal or flattened epithelium. Immunohistochemical and ultrastructural studies demonstrated that the lining cells were of mesothelial origin, and the diagnosis was benign cystic mesothelioma. In this paper, we present appropriate diagnostic and treatment procedures for benign cystic mesothelioma and discuss the particular usefulness of using immunohistochemical methods to achieve a histological diagnosis.