Overgrowth of the fat layer within the confines of the pericardial outline differentiates epicardial lipomatosis from pericardial lipoma, in which case the fat overgrowth is between the pericardium and the adjacent pleura. Similar to all other hyperplasia involving adipocytes, epicardial lipomatosis also may be related to obesity, steroid intake, etc. Usually of no clinical concern, excessive overgrowth has the potential to rarely produce pericardial tamponade.