Abstract
Since 1977, mesothelioma has been admitted as an occupational disease in the Federal Republic of Germany, if a previous exposure to asbestos at the working place can be proven. In practical work of pathologists the question arises as to how to proceed in the assessment of necropsy cases of mesothelioma, if the patient's occupational history is unknown. In this study, 100 necropsy cases of different exposure were examined by scanning electron microscopy. Concentration and length of fibers were used as criteria to distinguish between spontaneous and occupationally caused cases of mesothelioma. Calculation of the counting results showed that a distinction between the two groups is reliable when fibers >5 µm in length are counted.