Human malignant diffuse mesothelioma: submicroscopic study on the epithelial component.

A submicroscopic analysis of eight cases of malignant diffuse mesothelioma was performed. Unlike normal and hyperplastic mesothelium, well differentiated neoplastic cells were found to have a prominent RER and a conspicuous Golgi system. By using a postfixation in osmium ferrocyanide, an amorphous substance was observed in the extracellular space. These features may be related to the ability of malignant diffuse mesothelioma to produce large amounts of hyaluronic acid. The significance of groups of membrane bound dense bodies found in seven of eight cases examined is also discussed.