Mesothelioma-like tumors of the pleura: a review of 72 autopsy cases.

The 72 mesothelioma-like tumors of the pleura (MLTP) found among 33 500 autopsy cases collected over more than 30 years are reviewed. MLTP have a worse prognosis than the 106 cases of pleural mesothelioma autopsied in our institutes with regard to survival time and metastatic spread. In MLTP, adenocarcinomas predominate with a wide range of histological and cytological variation and prominent development of connective tissue having its origin in the periphery of the lung. These intrapulmonary primary tumors often fulfill the criteria of pulmonary scar cancer. Etiologically, there is no correlation between the origin of this tumor and smoking or exposure to asbestos. The absence of mucus formation and glandular differentiation, together with the presence of spindle-shaped carcinoma components and strong mesothelial or stroma proliferation, can make the differential diagnosis between this tumor type and mesothelioma difficult. Immunohistological investigations were performed on 11 cases with antibodies against intermediate filament proteins, vascular endothelium, collagen IV, macrophage antigens, carcinoembryonic antigen (CEA), LeuM1, and the antibody BerEP4. Our investigation shows that a battery of several tumor markers, such as antibodies against LeuM1, CEA, and the antibody BerEP4, as well as staining with periodic acid/Schiff/diastase discriminate primary from secondary pleural neoplasms, whilst intermediate filament proteins alone are of little diagnostic value.