In this latest fascicle DRs Churg, Cagle and Roggli concentrate on the cytopathologic and histopathologic features of diffuse malignant mesothelioma, it's many variants and other benign and malignant lesions to be distinguished from it. Histochemical, immunohistochemical, ultrastructural and molecular features of potential use in this differentiation are discussed and illustrated. Common differential diagnostic problems and their solutions take precedence, but all of the known benign and malignant lesions of serosal membranes are covered. Epidemiologic pathogenetic, clinical, radiographic and gross pathologic features are integrated with the discussions of these entities.