[Mesothelioma of the atrioventricular node and sudden death].

An incomplete atrioventricular block of grade III was detected by electrocardiography in a 3.5-year-old boy one week before his sudden death. On autopsy, cardiomegaly involving a 47% increase in heart weight and a moderate adaptational endocardial fibroelastosis were noted, as was a nodular tumor sized 6 X 3 X 1.5 mm at the atrioventricular node. The tumor was concluded to be a microcystic mesothelioma that had been destructive to the node and had begun infiltrating the cardiac muscle.