Hodgkin disease can involve diaphragmatic lymph nodes adjacent to the heart. When nodes at the cardiac apex are involved, the roentgenographic appearance simulates that of the normal pericardial fat pad. Though, to our knowledge, no cases have been reported in which this was the only intrathoracic manifestation of Hodgkin disease at the time the patient was first seen and the condition was diagnosed, it may be the only manifestation of relapse, as was true in the case presented.
Crowe JE. Cardiophrenic Adenopathy in Hodgkin Disease. Am J Dis Child. 1975;129(1):116-117. doi:10.1001/archpedi.1975.02120380086020