However, secondary signs, such as pleural effusion or erosion of the sternum are common in Hodgkin's disease while rare in the other masses. Calcification is rare. Computed tomography has proven useful in that it often will show that the apparently solid masses seen on plain film is actually composed of enlarged matted lymph nodes separated by well defined interfaces. Resection is not necessary, however, thoracotomy or mediastinoscopy are usually required to confirm the diagnosis. Chemotherapy or radiation are the common modes of treatment.
Prognosis varies with the histology.
The majority of mediastinal thyroid tissue is a substernal extension of a cervical goiter. On plain film the mass is well defined and homogeneous, causing smooth displacement and often narrowing of the trachea. Calcification is common. Although 131I studies are usually diagnostic and should be the first study to evaluate the suspected mass, false negative results occur. In the face of a negative radionuclide study but clinical suspicion of an intrathoracic goiter, a CT exam should be performed.