Patients with mediastinal masses can present in a variety of ways. A mediastinal mass is often an incidental diagnosis when patients undergo an evaluation for an unrelated condition or symptom. In some cases, patients present with complaints secondary to local mass effect on adjacent structures, such as respiratory symptoms due to airway compression or swelling due to compression of vascular structures. Other patients develop systemic symptoms that result from the mediastinal mass, which is discovered on subsequent work-up.
Benign or malignant mediastinal masses can develop from structures that normally are in the mediastinum or that pass through the mediastinum during development, as well as from metastases of malignancies that arise elsewhere in the body. A combination of clinical factors and imaging features often narrow the differential diagnosis when a mediastinal mass is detected. In some instances, the clinical and imaging features can be enough to guide therapy, which often includes surgical resection that provides a definitive diagnosis. Blood tumor markers can sometimes also support a specific diagnosis. In other cases, obtaining tissue via biopsy can be necessary to confirm a clinical suspicion prior to proceeding with therapy.
The approach to a patient with a mediastinal mass will be reviewed here, including planning the diagnostic work-up as well as initial therapy. In addition, a brief overview of the most common causes of mediastinal masses is presented. More detailed discussions of those pathologic processes are presented elsewhere.
The mediastinum is defined as “the space between the lungs”. The borders of the mediastinum are the thoracic inlet superiorly, the diaphragm inferiorly, the sternum anteriorly, the spine posteriorly, and the pleural spaces laterally.
The mediastinum is divided into compartments, and this is useful in developing a differential diagnosis when an abnormality is detected (table 1) as well as when planning techniques for biopsy or resection. The anterior, middle, and posterior compartments are relatively easy to define with radiographic studies (figure 1).