[A case report of so-called solitary fibrous tumor of the mediastinum].

A 52-year-old house wife was admitted to our hospital with the diagnosis of a impending rupture of the aneurysm of the ascending aorta. Chest X-ray showed an anterosuperior mediastinal mass which extended into right hemithorax and space between ascending aorta and superior vena cava on CT and MRI. Median sternotomy showed a large mass, arising from the left lobe of the thymus covered with mediastinal pleura and projecting into the right pleural cavity with no dissemination. The tumor was excised with the thymic glands together with the involved ascending aorta and pericardium. It was encapsulated tumor, 10 x 9 x 8 cm in size, 420 g in weight, and revealed central necrosis with bleeding on the cut surface. The pathological findings showed spindle cell tumor with high mitotic activity, immunoreactivity for vimentin, but not for keratin, and no ultrastructural evidence of micro villi. So far as the Japanese literature about the so-called solitary fibrous tumor of the mediastinum is concerned, this is considered to be the first case in our country.