The posterior mediastinum is bounded anteriorly by the posterior pericardium and extends posteriorly to the chest wall and laterally to include the costovertebral sulci. It contains the descending thoracic aorta, inferior vena cava and azygous veins, the sympathetic chains, and origins of the intercostal nerves at their nerve roots, and it is generally defined to include the esophagus and associated vagi as well. Most anatomic systems consider only lesions that are caudal to the fourth thoracic vertebral body to be within the posterior mediastinum, with more cephalad lesions resting within the superior mediastinum.

The majority of posterior mediastinal masses occurring in adults are benign. These lesions can be usefully classified according to whether they are cystic or solid on radiographic evaluation. Cystic masses in this region typically represent bronchogenic cysts (Fig. 15.1) or esophageal duplication cysts, whereas solid masses are most commonly benign neurogenic tumors (Figs. 15.2 and 15.3; e.g., schwannomas, neurofibromas, or ganglioneuromas). These neural tumors usually arise from the sympathetic chain or the proximal intercostal nerves, but sometimes the exact anatomical origin does not even become clear intraoperatively. Occasionally, one comes across a patient with a pheochromocytoma or paraganglioma, which arise from the randomly located mediastinal paraganglionic cells and may secrete hormones. At initial office evaluation, one should be alert to the presence of hypertension or palpitations that should dictate measurement of urine metanephrines. Esophageal leiomyomas (benign intramuscular tumors within the esophageal wall) are also generally grouped among the posterior mediastinal lesions. The approach to these lesions and to esophageal duplication cysts differs somewhat from the approach to lesions that are unassociated with the esophagus.

In many cases, posterior mediastinal masses come to light as asymptomatic radiographic abnormalities. They may uncommonly, however, present with signs of infection (in the case of infected cysts), or with dysphagia, chest pain, respiratory complaints, or neurological changes (e.g., Horner’s syndrome from tumors involving the upper sympathetic trunk; lower extremity symptoms from dumbbell tumors) resulting from mass effect on adjacent structures. Esophageal lesions can, of course, cause dysphagia but they too are often asymptomatic.

At present, because of the growing availability of less morbid, minimally invasive approaches to posterior mediastinal masses, most authors recommend resection even when lesions are asymptomatic. I believe that the recommendation about whether to proceed with resection of a posterior mediastinal mass needs to be individualized. Clearly, a symptomatic lesion is best managed by resection, except in unusual circumstances. When an asymptomatic lesion has all of the radiographic characteristics of a benign cyst or tumor (i.e., smooth margins, simpleappearing cyst material, minimally positron emission tomography PET) positive if PET has been done), then the age and general medical condition of the patient should be the key considerations. Since these lesions do generally grow—albeit at a fairly slow rate—it is likely that a young patient will eventually develop symptoms due to impingement on surrounding structures or infection of a cyst. Patients under the age of 60, then, who are otherwise good surgical candidates, are best managed by resection. For older patients, or those who have substantial comorbidities, it is perfectly reasonable to follow these benignappearing, asymptomatic lesions with radiographic studies and operate only if they begin to grow dramatically, the patient develops symptoms, or a change in radiographic appearance suggests malignancy. In any case, there is no urgency to remove these cysts and tumors. The significance of the very few reports of development of malignancy within a benign posterior mediastinal mass is likely overstated.