An autopsy case of a primary pericardial mesothelioma in a 53-year-old arc cutter is reported. He had often had the chance to inhale dust generated by sharpening the slate pencils composed of talc. He was admitted for heart failure due to pericardial tumor, but later died. The tumor was mainly located on the pericardium with a thickness of about 2.5 cm. Small nodular disseminations were observed in the left parietal pleura. Microscopically, tumor cells were epitheliallike and rich in histochemical demonstrable hyaluronic acid. Findings of immunohistochemical markers revealed keratin (+), EMA (+), calretinin (+), and CEA (-), which were characteristics of mesothelioma of epithelial type. The number of asbestos bodies (AB) in the lung parenchyma was increased (2,026 AB/gram dry lung tissue). Subsequent transmission electron microscopic examination equipped with an energy dispersive X-ray analyzer revealed that the fibers identified in the lungs were fibrous talc and actinolite. These findings suggested that this patient had been occupationally exposed to asbestos contaminated in the talc pencils, which induced the development of primary pericardial mesothelioma.Key words: Pericardial mesothelioma, Asbestos, Talc pencil, Fiber analysis Primary pericardial mesothelioma is an extremely rare and lethal cardiac tumor 1) . A correlation has been established between exposure to asbestos and the development of pleural and peritoneal mesothelioma in many epidemiological surveys 2) . However, the etiology of pericardial mesothelioma has not been elucidated. We report a case of pericardial mesothelioma occurring in an arc cutter who had used talc pencils, and examined the association between occupational exposure to asbestos and the development of this tumor by mineral analysis.A 53-years-old man was admitted to our hospital because of shortness of breath and leg edema. He had been working for an ironworks for 28 yr. He had used slate pencils composed of talc when he drew the lines of arc cutting on iron plates since he was 26 years-old. He had often inhaled the dust generated when sharpening the talc pencils using sandpaper without respirator. He had smoked 2 packs of cigarettes for 18 yr.Physical examination revealed distended jugular veins and leg edema. Breath sounds were decreased throughout the entire left lung field, but no fine crackle and no heart murmur was audible. His liver edge was palpable five fingerbreadths below the right costal margin.Chest radiography on admission revealed cardiac enlargement and bilateral pleural effusion (Fig. 1a). Computed tomographic scan of the chest revealed bilateral