Mediastinal tumors and cysts.

From a rather extensive review of the literature’2 and an analysis of the case records of patients subjected to operation for mediastinal tumors and cysts the following particular impressions were gained. These neoplasms are relatively infrequent. The most common primary types are those of the thymus and those arising from lymphatic tissues, dermoids and teratomas, and the neurogenous tumors. The cystic dermoids are more frequent than the more solid teratomas. Tumors of the sympathetic nerves are the most common type of neurogenous tumors. Bronchogenic cysts, fibromas, lipomas and intrathoracic goiters apparently occur somewhat less frequently than the above, while other tumors and cysts of this region seem to be exceedingly rare. The majority of the tumors are malignant and many of the benign ones are potentially malignant. It would appear that the majority of the tumors occurring in the mediastinum are those originating from lymphatic tissue and secondary malignant tumors which are not as yet amendable by surgical treatment. The other tumors and cysts are principally benign, though a group of primary malignant tumors other than of lymphatic origin occur in this region. Primary carcinoma is apparently less frequent than primary sarcoma but secondary sarcoma is rare in the mediastinum. Secondary carcinomas in the mediastinum occur most frequently from primary tumors elsewhere in the chest. The majority of thymic tumors are malignant, while many of the benign types, as well as an occasional malignant one, are associated with myasthenia gravis. The incidence of malignant tumors is estimated to be between 10 and 20 per cent in neurogenous tumors as well as in dermoids and teratomas. The incidence Is higher in the more solid teratomas than in the more cystic dermoids. A somewhat higher frequency of malignant degeneration Is thought to occur in fibromas and malignant degeneration is noted In other tumors of connective tissue. A malignant change in cysts other than dermoids would appear to be unusual but is occasionally noted in intrathoradic goiter (about 2 per cent). Small cell lymphosarcomas and gastro-enterogenous cysts occur clinically, as a rule, In infants and young children while malignant neurogenous tumors, lymphangiomas and bronchogenic cysts are