[Mesothelioma of the pleura--pathological anatomy]

The examination of the pathology of diffuse malignant mesotheliomas (DMM) is based upon the analysis of 600 pleural tumours of the German Mesothelioma Panel in Bochum. Macroscopically there is a characteristic feature of the tumour growth, often restricted to the pleura, with preference of the basal pleural parts even in advanced stages. The highly variable growth pattern of the tumour phenotype contains parts of epithelial cells (42%), sarcoma-like cells (18%), and biphasic patterns (27%) as revealed by microscopy. Secondary pleural carcinosis are much more frequent (10 x) as diffuse malignant mesotheliomas but may mimic the DMM. Since there is no specific tumour marker for DMM available, additional immunohistochemical staining using different monoclonal antibodies directed against cytokeratins and epithelial antigens are recommended especially for examinations of small biopsies. The morphological security cheque follows the criteria of the European Mesothelioma Panel and is subdivided into 5 groups: A, assured mesothelioma; B, possible mesothelioma; C, probable mesothelioma; D, possibly no mesothelioma; E, certainly no mesothelioma. In the Bochum panel the incidence of A and B is 66%, of C, 6% and of D and E, 28%. In addition to the histomorphological examinations, in dust analysis of nontumourous lung tissue an augmented asbestos charge has been found in approximately 90% of all cases. The significance of asbestos fibers as an essential cause of the pleural mesothelioma could be underlined by our own animal experiments. After instillation of asbestos fibers into the right lung, a transpleural transport of fibers was observed with preneoplastic lesions and transformation of multipotent subserosal cells.