An autopsy case of malignant mesothelioma associated with asbestosis

An autopsy case of malignant mesothelioma with asbestosis caused by asbestos exposure for 17 years is reported. Autopsy revealed that mesothelioma spread extensively in all serosal tissues including pleura, pericardium, diaphragm, peritoneum and tunica vaginalis testis. Histopathologically, most of the tumor showed an epithelial form, but sarcomatous and microcystic patterns were also observed. The tumor cells had abundant glycogen and hyaluronic acid and, immunohistochemically, they were positive for cytokeratin, vimentin and epithelial membrane antigen (EMA). Long, slender microvilli were characteristically observed in these tumor cells. All of these data were compatible with malignant mesothelioma. Procollagen type I (procol.I) immunostaining was performed to reveal the mesenchymal character of mesothelioma. Both epithelial‐type cells and sarcomatous‐type cells showed positive staining for procol.I, although the latter showed stronger immunoreactivity. Immunostaining for procol.I was found to be one of the useful tools for distinguishing mesothelioma from adenocarcinoma. Using an extraction method for asbestos fibers, asbestos bodies were found in many tissues including lymph nodes, liver, small intestine, spleen, kidney, testis and pleura, in addition to lung parenchyma. Although multiple tumor metastases from an undetermined primary site is not ruled out, ‘multifocal tumorigenesis’ is suspected from the widespread deposit of asbestsos fibers.