A 75-year-old woman presented with chest pain on exertion. Cardiac catheterization revealed double vessel coronary artery disease. Echocardiographic examination showed the presence of an abnormal mass in the interatrial septum without any flow velocity signal within the mass. She was scheduled for elective coronary artery bypass grafting. The lesion appeared as a homogeneous mass on CT scan, with an attenuation coefficient of -122 Hounsfield units, suggestive of lipoma. A T1-weighted MRI scan demonstrated that the signal intensity of the interatrial mass corresponded to that of fatty tissue. On surgery with cardiopulmonary bypass a large mass was found to involve the right atrial wall, the interatrial sulcus and the interatrial septum. The mass could not be resected completely, because it adhered strongly to the septal myocardium. On histological examination, the tumor was composed of mature fatty tissues, was not encapsulated and was diagnosed as infiltrating lipoma. The postoperative course was uneventful. CT, MR imaging and color Doppler ultrasonography were very useful in making a tissue-specific diagnosis.

A 75-year-old man was referred to our hospital with dyspnea on effort, recurrent attacks of loss of consciousness and abnormal shadow on chest X-ray film. Computed tomographic scan confirmed a 1.5×2.0cm mass with slight spiculation in the right lower lobe (S6) and revealed an ovoid right atrial mass. Transthoracic echocardiography showed that the giant mass which filled most of the right atrium had no mobility. Coronary angiography revealed clusters of new vessels which originated from the atrial branches of the circumflex coronary artery. A T1-weighted MRI scan demonstrated that the mass was isointense relative to the adjacent myocardium. We considered that performing cardiac surgery prior to pulmonary resection, as in a staged procedure, would have advantages in morbidity. We first performed removal of the right atrial tumor which was a 6.8×5.5×4.5cm shiny mass attached to the interatrial septum. Histological examination of the mass confirmed the diagnosis of cardiac myxoma. Three months later, right S⁶ segmentectomy was carried out using thoracoscopy and the tumor was finally diagnosed as squamous cell carcinoma. We have followed the patient for about 10 months after the first operation and there is no evidence of tumor recurrence and no more syncopic attacks.