- • Most mediastinal abnormalities are benign and
- • Division into anterior, superior, middle, and posterior “compartments” facilitates
- • More than 60% of lesions in adults are
in the anterior-superior mediastinum, whereas more than 60% in
children are in the posterior mediastinum.
- • Of masses, 75% in adults and 50% in
children are benign.
- • The most common malignant masses of the anterior-superior
mediastinum are thymoma, Hodgkin’s disease (HD), non-Hodgkin’s
lymphoma (NHL), and germ cell tumors.
- • Neurinomas are the most frequent tumor in the posterior
mediastinum and are often recognizable by their classic dumbbell-shaped
The finding of an abnormality on chest radiograph or chest computed
tomography (CT) most often prompts consideration of diseases of
the mediastinum. Findings may be incidental on a radiograph obtained
as part of the evaluation of an unrelated clinical issue (eg, suspected
pneumonia) or may be recognized on a study obtained to evaluate
a specific complaint, symptom, or sign directly referable to potential
mediastinal pathology (eg, swallowing difficulty) or after chest trauma
(eg, risk of dissection of the thoracic aorta). When present, symptoms
are related either to the primary disease process or to associated
compressive effects on regional anatomy. Thus, a symptom or sign
referable to a particular organ system may not be indicative of
primary disease in that system. For example, dysphagia may result
from either esophageal pathology or an extrinsic compressing mass.
Although there are no reliable estimates of prevalence, abnormalities
of structures within the mediastinum are varied and common. Many
abnormalities, such as courses or dilatations of otherwise normal
blood vessels, are benign structural variants, which are of no pathological
significance. Many nonmalignant lesions occur including pericardial
or bronchogenic cysts, aneurysmic dilatations of the aorta and great
vessels, benign tumors, and substernal goiters. Such lesions are generally,
but not always, asymptomatic. Malignant lesions may be either primary
or metastatic, and are equally likely to be symptomatic or asymptomatic.
Symptomatic lesions are most often malignant. Thymoma, germ cell
tumors, lymphoma, and neurinoma are the most common tumors of the
Anatomically, the mediastinum is the region of the body bounded
by the thoracic inlet superiorly, the diaphragm inferiorly, the
sternum anteriorly, the vertebral column posteriorly, and the pleura bilaterally
(Figure 24–1). Core elements of the respiratory,
digestive, and cardiovascular systems are located in this central
area as are elements of the neurological, lymphatic, and endocrine
Basic anatomy of the mediastinum. A: Anterior
view. B: Lateral view. C: Mediastinal divisions.
Separation of the mediastinum into anterior, superior, middle,
and posterior subdivisions, although not arbitrary, is somewhat
misleading in that there are no clear boundaries that separate ...