Sudden unexpected death accounts for 200,000-400,000 deaths each year in the United States. Although the vast majority of these fatalities are related to atherosclerotic heart disease, a small percentage (∼0.0025%) stem from primary cardiac neoplasms. There have been 120 cases of sudden death attributed to primary cardiac tumors in the (published) literature. Although 103 of these lesions were histologically benign (86%), their intracardiac locations precipitated conductive and hemodynamic abnormalities that resulted in sudden death. These tumors are usually easily recognized at necropsy. The most common intracardiac lesion causing sudden death, endodermal heterotopia of the atrioventricular (AV) node, however, may not be discovered unless the AV node is microscopically examined. Owing to the rarity of these neoplasms, a brief review of their salient gross and microscopic features is in order.