Benign cystic peritoneal mesothelioma.

The well defined but rare entity of benign cystic mesothelioma is reported. The aetiology of this neoplasm remains obscure. The presenting features make a precise preoperative diagnosis difficult; information provided by computed tomography and cytology may help. A firm diagnosis can only come from electron microscopic or immunohistochemical examination of the tumour. Diagnostic accuracy and diligent follow up are essential because, although the tumour is considered benign, it does tend towards local recurrence.