Abstract
The purpose of this paper is to report a group of nine cases of acute leukemia with large mediastinal tumors or infiltrations, and the results of roentgen therapy on this condition. While the occasional presence of such tumor masses in acute leukemia has been recognized, the lack of any but casual reference to them in standard texts indicates that they are considered rare. It is becoming increasingly evident, however, that a definite proportion of patients with acute leukemia have mediastinal masses which tend to give characteristic symptoms of pressure. These tumors may precede the typical blood changes, and, in my observation, they have been the most common form of massive mediastinal enlargement in children. Localized tumor masses composed of round sarcoma-like cells have at times been observed at necropsy in patients dying of acute leukemia. These have been noted most frequently in the anterior mediastinum and have usually been considered