# 14 - 306 Disorders of the Mediastinum

### 306 Disorders of the Mediastinum

patients. Nearly all patients with secondary pneumothorax should be 
treated with tube drainage. Many will need thoracoscopy or thora­
cotomy with stapling of blebs and surgical pleurodesis. If the patient is 
not a good operative candidate or refuses surgery, chemical pleurodesis 
should be considered.
Traumatic Pneumothorax 
Traumatic pneumothoraces can result 
from both penetrating and nonpenetrating chest trauma. Traumatic 
pneumothoraces are usually treated with tube drainage unless they are 
very small. If a hemopneumothorax is present, one chest tube might be 
placed in the superior part of the hemithorax to evacuate the air and 
another in the inferior part of the hemithorax to remove the blood. 
Iatrogenic pneumothorax is a type of traumatic pneumothorax that is 
becoming more common. The leading causes are transthoracic needle 
aspiration, thoracentesis, and complications of the insertion of central 
intravenous catheters. Most can be managed with supplemental oxygen 
or aspiration, but if these measures are unsuccessful, tube drainage 
should be performed.
Tension Pneumothorax 
This condition usually occurs during 
mechanical ventilation or resuscitative efforts. The positive pleu­
ral pressure is life-threatening both because ventilation is severely 
compromised and because the positive pressure is transmitted to the 
mediastinum, resulting in decreased venous return to the heart and 
reduced cardiac output. Difficulty in ventilation during resuscitation or 
high peak inspiratory pressures during mechanical ventilation strongly 
suggest the diagnosis. The diagnosis is made by physical examination 
showing an enlarged hemithorax with no breath sounds, hyperreso­
nance to percussion, shift of the mediastinum to the contralateral side, 
and hypotension. Tension pneumothorax must be treated as a medical 
emergency. If the tension in the pleural space is not relieved, the patient 
is likely to die from inadequate cardiac output or marked hypoxemia. 
A large-bore needle should be inserted into the pleural space through 
the second anterior intercostal space. If large amounts of gas escape 
from the needle after insertion, the diagnosis is confirmed. The needle 
should be left in place until a chest tube can be inserted.
Acknowledgment
Richard W. Light contributed to this chapter in the 21st edition and some 
material from that chapter has been retained here.
■
■FURTHER READING
Feller-Koppman D, Light R: Pleural disease. N Engl J Med 378:740, 
2018.
Light RW: Pleural Diseases, 6th ed. Lippincott, Williams and Wilkins, 
Baltimore, 2013.
Rahman NM et al: Intrapleural use of tissue plasminogen activator 
and DNase in pleural infection. N Engl J Med 365:518, 2011.
Roberts ME et al: British Thoracic Society Guideline for pleural dis­
ease. Thorax 78:1143, 2023.
Stefi F. Lee, Rebecca M. Baron, 

Hilary J. Goldberg

Disorders of the 

Mediastinum
The mediastinum is the region between the pleural sacs bound by the 
thoracic inlet superiorly and the diaphragm inferiorly. It is separated 
into three compartments, and diseases can arise from the anatomical 
structures residing in each respective compartment (Fig. 306-1). The 
anterior mediastinum comprises the retrosternal space anterior to the 
pericardium and brachiocephalic vasculature; it contains the thymus 

Disorders of the Mediastinum 
CHAPTER 306
FIGURE 306-1  Sagittal chest CT of the mediastinum and its three separate 
compartments.
gland, the anterior mediastinal lymph nodes, and the internal mam­
mary arteries and veins, and can give rise to several neoplasms. The 
middle mediastinum lies between the anterior and posterior medias­
tina and contains the heart; the ascending and transverse arches of 
the aorta; the venae cavae; the brachiocephalic arteries and veins; the 
phrenic nerves; the trachea, the main bronchi, and their contiguous 
lymph nodes; and the pulmonary arteries and veins. The posterior 
mediastinum extends from the posterior border of the heart and 
trachea to the vertebral column posteriorly. It contains the descend­
ing thoracic aorta, the esophagus, the thoracic duct, the azygos and 
hemiazygos veins, and the posterior group of mediastinal lymph nodes. 
Disorders of the mediastinum encompass a broad range of diseases 
including but not exclusive to neoplastic and nonneoplastic masses, 
congenital or acquired malformations of anatomical structures, infec­
tions, and chronic fibrosing mediastinitis, which will be addressed in 
this chapter.
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■MEDIASTINAL MASSES
The first step in evaluating a mediastinal mass is to place it in one of the 
three mediastinal compartments, since each has different characteris­
tic lesions (Table 306-1). The anterior mediastinum can give rise to 
neoplasms including thymomas, germ cell tumors, teratomas, lympho­
mas, and thyroid goiter. Thymomas are the most common neoplasm 
in the anterior mediastinum and are closely tied to paraneoplastic 
syndromes, most notably, myasthenia gravis, the diagnosis of which 
is supported by the presence of serum anti-acetylcholine receptor 
antibodies. Teratomas, the most common type of germ cell tumor, are 
multilobulated cystic lesions that contain fat, soft tissue, and calcium. 
Elevated tumor markers, α fetoprotein and β-human chorionic gonad­
otropin, distinguish between seminomatous and nonseminomatous 
germ cell tumors, which can guide treatment. Seminomas are generally 
responsive to radiation therapy, whereas nonseminomatous germ cell 
tumors are treated with standard chemotherapy. Computed tomogra­
phy (CT) scanning is an important imaging technique for evaluating 
mediastinal masses as it can attenuate fat, water, calcifications, and air 
in most instances. Diffusion-weighted magnetic resonance imaging 
aids in improved tumor characterization and differentiation between 
cystic and solid structures. Lymphomas appear as homogeneous soft

TABLE 306-1  The Three Compartments of the Mediastinum
 
ANTERIOR COMPARTMENT
MIDDLE COMPARTMENT
POSTERIOR COMPARTMENT
Anatomical boundaries
Manubrium and sternum anteriorly; 
pericardium, aorta, and brachiocephalic 
vessels posteriorly
Anterior mediastinum anteriorly; posterior mediastinum 
posteriorly
Contents
Thymus gland, anterior mediastinal 
lymph nodes, internal mammary 
arteries, and veins
Pericardium, heart, ascending and transverse 
arch of aorta, superior and inferior vena cavae, 
brachiocephalic arteries and veins, phrenic nerves, 
trachea, and mainstem bronchi and their contiguous 
lymph nodes, pulmonary arteries, and veins
Common abnormalities
Thymoma, lymphomas, teratomatous 
neoplasms, thyroid masses, parathyroid 
masses, mesenchymal tumors, giant 
lymph node hyperplasia, hernia through 
foramen of Morgagni
Metastatic lymph node enlargement, granulomatous 
lymph node enlargement, pleuropericardial cysts, 
bronchogenic cysts, masses of vascular origin
PART 7
Disorders of the Respiratory System
tissue structures and can present at various stages. At more advanced 
stages, lymphomas can present with anterior and middle mediastinal 
lymphadenopathy. Mediastinoscopy is often performed for sampling of 
paratracheal and subcarinal lymph nodes. Biopsy can also be achieved 
via percutaneous fine-needle aspiration or endoscopic transesophageal 
or endobronchial ultrasound. Scintigraphy with radioactive iodine 
scan can efficiently establish the diagnosis of an intrathoracic goiter 
that can also lie in the anterior mediastinum.
Surgical resection is the mainstay of treatment for most anterior 
mediastinal masses like in localized early stages of thymic carcinomas, 
symptomatic teratomas, and mediastinal goiters. Lymphoma is treated 
with multimodal therapy with a combination of radiation and chemo­
therapy; surgery is rarely indicated. Ultimately, the involvement of a 
multidisciplinary interprofessional team of oncologists, pulmonolo­
gists, radiologists, and cardiothoracic surgeons is necessary to guide 
best treatment practices and provide personalized care for each patient.
The middle mediastinum consists of central vascular and broncho­
genic structures. Most middle mediastinal masses are benign and result 
from abnormalities in embryonic development, such as bronchogenic 
cysts (that arise from abnormal ventral foregut budding), duplication 
cysts (that arise from persistent diverticulum of the dorsal bud of the 
foregut), and pericardial cysts (that arise from abnormal fusion of 
pericardial recesses). In contrast, advanced stages of malignancy often 
do not remain localized within one compartment and can traverse 
borders through hematogenous and lymphatic spread (Fig. 306-2). It 
is also important to note that, due to the presence of central vasculature 
in the middle mediastinum, disruption of these structures can lead to 
acute life-threatening disease. For example, superior vena cava (SVC) 
syndrome is a medical emergency that presents with severe dyspnea 
and facial and upper extremity edema from venous distension because 
of compression of the SVC. SVC obstruction often occurs due to a 
FIGURE 306-2  Bronchoscopic view of main carina with a malignant mass 
encroaching on the right mainstem airway. (Courtesy of Dr. Majid Shafiq.)

Pericardium and trachea anteriorly; 
vertebral column posteriorly
Descending thoracic aorta, esophagus, 
thoracic duct, azygos and hemiazygos 
veins, sympathetic chains, and the 
posterior group of mediastinal lymph 
nodes
Neurogenic tumors, meningocele, 
meningomyelocele, gastroenteric 
cysts, esophageal diverticula, hernia 
through foramen of Bochdalek, 
extramedullary hematopoiesis
malignant process; lung cancer, particularly small-cell lung carcinoma, 
accounts for up to 50% of cases. Endovenous recanalization, usually 
performed via an interventional radiology approach, restores venous 
return and reduces the risk of respiratory failure and death.
Neurogenic tumors are the most common cause of posterior 
mediastinal tumors. They may arise from peripheral, autonomic or 
paraganglionic nervous systems and are often benign. Other causes 
include diaphragmatic hernia, meningoceles, esophageal diverticula, or 
extramedullary hematopoiesis. Barium studies of the gastrointestinal 
tract are indicated in many patients with posterior mediastinal lesions 
because hernias, diverticula, and achalasia are readily diagnosed in this 
manner. Finally, mediastinal masses have a wide spectrum of disease 
severity, for which reason it may be difficult to determine the best 
course of action. When presented with a mediastinal mass, considering 
factors such as clinical symptoms, age of the patient, and location of 
the mediastinal tumor helps to determine the likelihood of malignancy 
and need for intervention.
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■ACUTE MEDIASTINITIS
Mediastinitis refers to an acute inflammatory and/or infectious condi­
tion involving the mediastinum. Cases of acute mediastinitis are usually 
due to esophageal perforation, occur after median sternotomy for cardiac 
surgery, or are seen related to infections descending from the neck, oral 
cavity, or facial area. Patients with esophageal rupture are acutely ill with 
chest pain and dyspnea due to the mediastinal infection. The esophageal 
rupture can occur spontaneously or as a complication of esophagoscopy 
or the insertion of a Blakemore tube. Appropriate treatment consists of 
exploration of the mediastinum with primary repair of the esophageal 
tear and drainage of the pleural space and the mediastinum.
The incidence of mediastinitis after median sternotomy is 0.4–5.0%. 
Patients most commonly present with wound drainage. Other pre­
sentations include sepsis and a widened mediastinum. The diagnosis 
usually is established with mediastinal needle aspiration. Treatment 
includes immediate drainage, debridement, and parenteral antibiotic 
therapy, but the mortality rate still exceeds 20%.
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■CHRONIC MEDIASTINITIS AND 

FIBROSING MEDIASTINITIS
The spectrum of chronic mediastinitis ranges from granulomatous 
inflammation of the lymph nodes in the mediastinum to fibrosing 
mediastinitis. Most cases of fibrosing mediastinitis follow a history of 
granulomatous infections, commonly due to histoplasmosis or tubercu­
losis, but sarcoidosis, silicosis, and fungal diseases are at times causative. 
Patients with granulomatous mediastinitis are usually asymptomatic. 
Those with fibrosing mediastinitis usually have variable symptoms 
depending on the extent and location of invasion of mediastinal struc­
tures such as the SVC or large airways, phrenic or recurrent laryngeal 
nerve paralysis, or obstruction of the pulmonary artery or proximal 
pulmonary veins. Fibrosing mediastinitis can be devastating in severe 
cases. Common clinical manifestations include dyspnea, chest pain, SVC 
syndrome, hemoptysis, dysphagia, and Horner’s syndrome. Diagnosis 
involves a combination of clinical, radiologic, and histopathologic find­
ings. Imaging modalities such as CT and magnetic resonance imaging