Mediastinal masses cause interesting problems from the point of diagnosis and treatment. Especially for the past twenty years, developments in radiology, computerized tomography, magnetic resonance imaging, radioisotopic scanning, immunohistochemical diagnosis, radioimmunassay, technics of electronmicroscopy; availablity of percutaneous needle biopsy; digital subtraction angiographgy (DSA); etc have been very useful for the identification of the type and size of the mass and it's relation with the neighboring organs, preoperativly and they have caused primary surgical intervention to be used more selectively. Improvements in surgical and anesthesiological techniques have decreased the rate of operative morbidity and mortality. Developments in radio and chemotherapy not only cause the treatments of some tumors such as lymphoma and germ cell tumors to be possible without a surgical intervention but also they provide a good survival rate to the patients having malignant tumors with the help of well investigation of the biopsy specimens.

In our department for the past seventeen years, 262 cases of mediastinal mass had been diagnosed and treated. Of them, 211 cases were excluded because of secondary mass. In this report we present the results of 51 cases of primary mediastinal mass which were investigated according to the principals mentioned above.