Abstract
A multicystic mesothelioma of the omentum in a 36 year old woman consisted of a multicystic mass with foci of typical endometriosis and ‘necrotic pseudoxanthomatous nodules’. The presence of endometriosis within multicystic mesothelioma has never been reported. Our findings support the hypothesis that endometriosis plays a role in the pathogencsis of multicystic mesothelioma and that this is a reactive rather than a neoplastic lesion.