Malignant Mesothelioma in Japan: Analysis of Registered Autopsy Cases

In the Annual of the Pathological Autopsy Cases in Japan, issued by the Japanese Society of Pathology from 1958 to 1996, a total of 1,846 (0.17%) malignant mesothelioma cases (1,287 male, 558 female, 1 unknown) were registered among 1,056,259 autopsy cases. The frequency of mesothelioma (number of cases/total autopsy cases) was 0.10% (461/440,334) for the term 1958-1979, 0.18% (716/390,124) for 1980-1989, and 0.30% (669/225,801) for 1990-1996; the frequency of cases increased significantly over the time periods (p < .0001). Among 1,785 cases for which tumor sites were ascertained, there were 1,213 pleural mesothelioma (68.0%), 431 peritoneal (24.1%), 108 pericardial (6.1%), 6 tunica vaginalis testis (0.3%), and 28 "others" (1.6%). Histological cell type was noted in 598 cases; 245 (41.0%) were epithelial, 168 (28.1%) were biphasic, and 185 (30.9%) were sarcomatous. Seventy-three (0.007%) cases of malignant mesothelioma with asbestosis were found during the entire 39-y period. The frequency of those with asbestosis (number of cases/total autopsy cases) was 0.001% (5/440,334) for the term 1958-1979, 0.006% (27/390,124) for 1980-1989, and 0.018% (41/225,801) for 1990-1996; this increase over time was statistically significant (p < .0001). Researchers expect that cases of asbestos-related mesothelioma will increase in Japan in the future. Tumor sites and histological cell types of mesothelioma with asbestosis did not differ from those in individuals without asbestosis.