Download Anterior mediastinal masses

R vd Berg
3 Feb 2012
 25
year old male
 HIV
 Seen 1/12 ago with a right pleural
effusion
 Started on TB-treatment
 Now presents with a mediastinal mass &
right pleural effusion
 For CT chest
 ? Lymphoma
Differentiating pulmonary from
mediastinal masses:
Mediastinal Mass
Epicenter in mediastinum
Pulmonary Mass
Epicenter in lung
Obtuse angles with the lung Acute angles
No air bronchograms
Air bronchograms possible
Smooth and sharp margins
Irregular margins
Movement with swallowing Movement with respiration
Bilateral
Unilateral
Anatomical division & content:
Anterior mediastinum:
Thymus, lymphnodes, adipose tissue, and internal mammary vessels
Thyroid
Middle mediastinum:
Heart, pericardium, aorta, SVC, IVC, brachiocephalic vessels, pulmonary
vessels, trachea, main bronchi, lymph nodes, N.phrenic, N.vagus, N.left
recurrent laryngeal
Posterior mediastinum:
Oesophagus, descending aorta, azygos & hemiazygos veins, thoracic duct,
vagus and splanchnic nerves, lymph nodes, fat
Paraspinal structures
Anterior Mediastinum:
Anterior Junction Line:
 Seen in 25% cases
 Four layers of pleura separating the lungs behind the upper two-thirds
of the sternum.
 Runs obliquely from upper right to lower left and does not extend
above the manubriosternal junction (T4/5).
 Anterior masses in the prevascular region can obliterate the anterior
junction line, with preservation of more posterior lines.
Hilum overlay sign:
 Normal hilar structures project through a mass, such that the mass
can be understood as being either anterior or posterior to the
hilum
 Preservation or disruption of posterior mediastinal lines can help
further clarify the location of the mass
(a) Mass is either anterior or posterior to the hila. Descending aorta is clearly seen, indicating that the mass is not within the
posterior mediastinum.
(b) Anterior mediastinal mass. Anterior junction line is obliterated, whereas the lung interfaces with the hilar vessels (arrow)
and aorta (arrowhead) are preserved.
Epicardial fat pad
Right paratracheal stripe:
 Formed by the trachea, mediastinal connective tissue, and
paratracheal pleura, visible due to the air–soft tissue
interfaces on either side, seen projecting through the SVC.
 <5mm.
 Can be widened due to abnormality of any of its
components, from the tracheal mucosa to the pleural space.
 Azygos vein lies at the inferior margin of the right
paratracheal stripe at the tracheobronchial angle.
(a) Goiter (arrow) extending into the middle mediastinum, obliterating the right
paratracheal stripe, causing deviation of the trachea to the left (black arrowhead).
Above the level of the clavicles, the margins of the mass are not sharp (white
arrowhead), indicating that the mass has an anterior mediastinal
component.
Lymphadenopathy:
(a) Right paratracheal stripe is not seen, having been obliterated by a right
paratracheal mass (arrowheads).
Aortic-pulmonary window:
 From aortic arch to the pulmonary artery inferiorly.
 Should have a concave or straight border with the adjacent lung.
Aortic-pulmonary reflection:
 More anterior, from the aortic arch to the level of the left main
bronchus, where it usually continues as the border of the left side
of the heart.
 Represents the interface between the lung and mediastinum along
the main pulmonary artery
AP window lymphadenopathy
Aneurysm of the aortic arch
Azygoesophageal recess & line:
 Interface between right lung and mediastinal reflection
inferior to the arch of the azygos vein, with the oesophagus
lying anteriorly and the azygos vein posteriorly within the
mediastinum.
 Has an interface with the middle mediastinum; thus, the
resulting line seen can be interrupted by abnormalities in
both the middle and posterior compartments.
Bronchogenic cyst. (a) Subcarinal mass (*), splaying of the carina, and abnormal
convexity of the upper and middle thirds of the azygoesophageal line (arrowheads).
Posterior junction line:
Posterior mediastinal line that is seen above the level
of the azygos vein and aorta and that is formed by
the apposition of the pleura posterior to the
oesophagus and anterior to the vertebral bodies.
 Above the suprasternal notch and lies almost
vertical, other than anterior jx line.

Cervicothoracic sign:


The anterior mediastinum stops at the level of the superior
clavicle.
Therefore, when a mass extends above the superior clavicle, it is
located either in the neck or in the posterior mediastinum.
The paraspinal lines:


Interface between lung and the pleural reflections over the
vertebral bodies.
The left paraspinal line runs parallel to the lateral margin of the
vertebral bodies and can lie anywhere medial to the lateral wall of
the descending aorta (seen due to the interface between the
lateral aortic margin and the lung). The right paraspinal line lies
within a few millimeters of the vertebrae.
Paraspinal abscess. (a) Mass (arrow) effacing the left paraspinal line. The lateral
wall of the descending aorta is seen as a separate entity (arrowhead).
Descending aortic aneurysm. (a) Lateral displacement of the lateral margin of the
descending thoracic aorta.
Neurogenic tumor. (a) Small mass (arrow) disrupting the left paraspinal line
inferiorly.
Extramedullary haematopoeiesis in Thalasemia:
Bilateral paraspinal masses with round, lobulated margins.
Medullary expansion of the bony structures with widening of the ribs.
Decide whether lung or mediastinal mass.
No tissue planes separating the mediastinum & lesions can occur in
more than compartment.
Anterior mediastinal masses:
 Hilum overlay sign + preservation of the posterior mediastinal
lines .
Middle mediastinal masses:
 Widening of the right paratracheal stripe and convexity of the AP
window .
Middle or posterior mediastinal masses:
 Disruption of the azygoesophageal recess .
Posterior mediastinum:
Obliteration of the post junctional line.
Paravertebral masses :
 Disruption of the paraspinal lines.
Masses above the clavicles :
 Posterior masses have sharp margins due to their interface with
lung, whereas anterior masses do not.
26/12/2011
14/11/2011
(42 days earlier)
26/11/2011
26/12/2011
30/11/2011


A Diagnostic Approach to Mediastinal Abnormalities,Whitten CR
et al, Radiographics, May 2007, p.657-671
Mediastinal Masses : localize and characterize, Bhalla S,
Hazewinkel M and Smithuis R, 2007, www.radiologyassistant.nl

Some radiographs from www.learningradiology.com

Primer of Diagnostic Imaging, Weissleder, et al, 4th ed, 2007.