[Cardiac liposarcoma at the right ventricular outflow tract (RVOT) following lipomatous hypertrophy of the interatrial septum (LHIS); report of a case].

: A 23-year-old man, presenting with a 10-year history of a cardiac lipoma (lipomatous hypertrophy of the interatrial septum: LHIS), complained of anterior chest discomfort. Echocardiography and magnetic resonance imaging revealed remarkable hypertrophy of the interatrial septum (IAS) and posterior wall of the right atrium (RA), massive pericardial adipose tissue, and mild aortic valve insufficiency caused by compression of the tumor on the right ventricular outflow tract (RVOT). We performed surgical resection of the tumor stemming from the RVOT following removal of a large amount of the pericardial fat tissue (1,794 g), and then undertook biopsies of the IAS and the posterior wall of the RA. Pathological examination showed the right ventricular (RV) tumor to be liposarcoma and confirmed the benign nature of the biopsy tissues. We herein report a rare case of cardiac liposarcoma following LHIS in a young patient.