A case report of "lipomatous hypertrophy of the cardiac interatrial septum", with a proposal for a new term "lipomatous hamartoma of the cardiac atrial septum".

An autopsy case of "lipomatous hypertrophy of the cardiac interatrial septum" (LHIS) combined with marked stenosis and calcification of the aortic and mitral valves due to fibrous valvular endocarditis, malignant lymphoma, and mucin-producing cancer of the pancreas is reported. LHIS and mucin-producing cancer of the pancreas were incidental findings at autopsy. Microscopically, the LHIS in this case consisted of proliferation of mature fat cells, brown fat cells and cardiac muscle cells. Since these three cell types are normal structural components of the interatrial septum, it was considered that the LHIS was a hamartomatous rather than hypertrophic lesion, of the cardiac atrial septum. Accordingly it was concluded that the term "lipomatous hamartoma of the cardiac atrial septum" was more appropriate for this lesion in the case presented here. As far as we know, this is the first reported case of LHIS in Japan.