ONLY in the past twenty years has it been possible to treat mediastinal tumors successfully. Before that the rarity of the tumors and the difficulty of accurate diagnosis, plus the lack of properly developed surgical technic, caused the mediastinum to be considered unapproachable, surgically speaking. Since symptoms were not alarming, except in cases of advanced malignant lymphomas, therapy, if any, consisted solely of irradiation. No attempt was made to determine either the type of tumor or its sensitivity to radiation. Indeed, exploration was considered only in instances in which alarming complications such as tracheal obstruction, bronchial perforation or secondary infection forced the physician to exhibit more than passive interest. Unquestionably the rapid advances in the field of thoracic surgery and the routine use of roentgenograms of the chest have completely changed the physician's attitude toward these tumors. They certainly occur more frequently than it was formerly believed. Blades,1in