THE extra-pulmonary and extra-mediastinal tumors of the thorax include a large variety of uncommon lesions, for the most part rare in the experience of the clinician, the roentgenologist, or the pathologist. For the purpose of this symposium an artificial relationship based on location has been imposed. In such an heterogeneous mixture, it has been difficult to deduce any semblance of reasonable relationship between the individual types of tumors. The following arrangement, by origin as well as location, may serve to orient the reader in some degree. I. Tumors of the thoracic wall proper: a. Non-malignant primary neoplasm; b. Malignant primary neoplasm; c. Metastatic malignant neoplasm; d. Ganglionic neuroma and neurofibroma. II. Tumors of the pleura: a. Extrinsic source; 1. Metastatic malignancy, 2. Hydatid, 3. Tuberculoma, 4. Fibrinoma. b. Intrinsic source; 1. Endothelioma of pleura, 2. Chondroma of pleura. III. Tumors of other local origin: a. Aneurysm of the innominate artery; b. Embryonal rests; c. Primary carcinoma of the pulmonary apex (superior pulmonary sulcus tumor). I.—Tumors of the Thoracic Wall Proper (a) The large group of non-malignant primary neoplasms of the thoracic wall includes the tumorous hyperplasias on any one or more of the mesodermal derivatives which are involved in the formation of the wall proper, such as lipoma, fibroma, myxoma, chondroma, osteochondroma, and angioma. As a group, these non-malignant thoracic wall tumors will present a prolonged history of known mass, and pain, dependent upon the degree of pressure on intercostal nerves or pleura. Dyspnea is present only if the tumor should attain sufficient size to embarrass the respiratory function. Pleural effusion is uncommon. These masses may obscure the underlying pulmonary fields in a degree corresponding to their thickness and specific density. As a rule they will be found as rather sessile tumors, sharply marginated, and homogeneous in character of shadow. Both fibroma and myxoma have been reported as presenting, both externally and internally, as a “collar-button mass,” or as spreading the ribs apart by the intercostal tumefaction. Chondroma, osteochondroma, and osteoma are rather familiar to the roentgenologist. They are most common in individuals who have multiple osteochondromas of the familial type. Roentgenographically, the last two present architectural characteristics which distinguish them definitely from the other connective tissue tumors. Similar comment applies to benign giant-cell tumor of the rib. The angioid neoplasms present certain changes which may serve to distinguish them.