Imaging in mediastinal masses

1. IMAGING IN MEDIASTINAL PATHOLOGIES
Dr. Milan Silwal
Resident, MD Radiodiagnosis
NAMS

2. Presentation Outline
• Relevant radiological anatomy
• Mediastinum: Division
• Imaging methods for mediastinum
• Approach to mediastinal pathologies
• Pathologies according to the divisions
• Summary

3. • The mediastinum is a space in the thorax that lies in
the midline of the chest between the pleura of
each lung and extends from the sternum to
the vertebral column.
Relations
• superiorly - continuous with the loose connective
tissue of the neck
• anteriorly - chest wall
• laterally - lungs and pleura
• posteriorly - thoracic spine
• inferiorly - diaphragm

4. Divisions
• Numerous methods; the most common of which
include the Shields’ classification scheme used in
clinical practice and the traditional, Fraser and Pare,
Felson, Heitzman, Zylak, and Whitten models used in
radiologic practice
 Anatomical classification
 Sutton classification
 Felson classification
 ITMIG classification

5. A. Anatomical classification
• superior mediastinum: above upper
level of the pericardium and plane
of Ludwig
• inferior mediastinum: below
the plane of Ludwig
– anterior mediastinum: anterior
to the pericardium
– middle mediastinum: within the
pericardium
– posterior
mediastinum: posterior to the
pericardium

6. B. Sutton classification
• Anterior division: in front of
the anterior pericardium and
trachea,
• Middle division: within the
pericardial cavity but
including the trachea.
• posterior division: lies
behind the posterior
pericardium and trachea.

7. C. Felson classification:
• Anterior: from the sternum
to the posterior aspect of the
heart and great vessels.
• Middle: The compartment
posterior to the heart and
great vessels, to a line
drawn 1 cm posterior to the
anterior edge of the thoracic
vertebrae.
• Posterior: The space behind
the posterior limit of the
middle mediastinum.

8. D. ITMIG classification

9. Shields’ classification

10. Heitzman classification
It describes 6 compartments: the thoracic inlet, the anterior mediastinum, the
superior aortic area (above the aortic arch), the infra-aortic area (below the
aortic arch), the supra-azygos area, and the infra-azygos area

11. Imaging methods
• CXR
• Barium Swallow
• CT
• MRI
• USG
• Radionuclide scan
• PET

12. • Mediastinal abnormalities often manifest initially at
conventional radiography.
• CT will be made to further analyze and characterize
anterior and middle mediastinal masses.
• An MRI is usually made to analyze masses located in
the posterior compartment because the majority of
these masses turn out to be neurogenic in nature.

13. CXR
• high kVp (120-150 kVp) technique
• A specially designed wedge filter with its thickest
portion over the lung and thinnest portion over the
mediastinum achieves appropriate exposure of the
mediastinum without over exposing the lungs.
• May appear normal or present as mediastinal
widening

14. Barium swallow
• oesophageal displacement help localize a mass
• hernias and oesophageal tumours can be
definitively diagnosed.

15. Computed tomography (CT)
• Useful for
– localizing mass
– demonstrating the extent masses
– Characterize nature of mass
• Fat and some fluid-filled masses are readily
differentiated from solid tumours
• aneurysms and anomalous vessels can be precisely
diagnosed in CECT.

16. • CT better demonstrates
– Calcification within a mass
– invasion of the mediastinal fat, indicating malignant rather
than benign disease
– resectibility of mediastinal masses
• Also helpful
– for guided FNAC/biopsy
– To guide treatment and F/U for the response to therapy.

17. MRI
• major uses:
– to demonstrate the status of the larger intrathoracic blood
vessels, notably in patients with superior vena caval
obstruction or aortic aneurysms,
– Particularly helpful for posterior mediastinal masses.
– also to differentiate between vessels and LN where contrast
injection is contraindicated
• MRI is useful for demonstrating any intraspinal
extension of mediastinal masses

18. MRA
• to demonstrate intrinsic disorders of the major
intrathoracic blood vessels and
• to demonstrate stenosis, distortion, and
displacement of vessels by mediastinal masses
and other mediastinal processes

19. USG
• particularly helpful in distinguishing cysts from solid
masses in contact with the intercostal spaces;
• to distinguish cardiac from paracardiac masses
• to guide mediastinal biopsy
• Approaches: Transthoracic, parasternal or
suprasternal

20. Endoscopic US
• demonstrates lymph nodes and other masses adjacent
to the oesophagus
• can show the aortic arch and descending aorta,
notably for the diagnosis of aortic dissection and
aortic aneurysms.
• Future applications may include
– bronchoscopic US for staging assessment and needle
aspiration of mediastinal and hila nodes.

21. Radionuclide examinations
• rarely been used for mediastinal disorders,
• Conventional techniques can be helpful in deciding
whether a mediastinal mass is due to ectopic thyroid
tissue by using sodium iodide
• Neuroendocrine tumours and phaeochromocytomas
can be demonstrated by somatostatin receptor
scintigraphy

22. • radio-iodine MIBG(metaiodobenzylguanidine)
imaging is very useful when searching for extra-
adrenal intrathoracic phaeochromocytomas.
• Gallium scanning may be of use in evaluation of the
mediastinum in adults with sarcoidosis or children
with lymphoma.

23. PET
• PET scanning using [fluorine 18]flouro-2-deoxy-D-
glucose (FDG)
• more accurate than CT or MRI for diagnosing
mediastinal lymph node metastases from
bronchogenic carcinoma.

24. Related pathology
• Broadly, pathology that affects the
mediastinum can be divided into those that
result in a focal mass, or those that result in
diffuse disease involving the mediastinum.
• Additionally, air may track into the
mediastinum in pneumomediastinum.

25. • D/D of a focal mediastinal mass is highly
dependant on its location within the
mediastinum, resulting in specific differential lists
for
• thoracic inlet masses
• anterior mediastinal masses
• middle mediastinal masses
• posterior mediastinal masses

26. Diffuse mediastinal disease can be separated into groups
depending on whether the mediastinal disease is smooth or
lobulated:
o smooth
 mediastinal lipomatosis
 mediastinal malignant infiltration
 mediastinal haemorrhage
 mediastinitis
o lobulated
 mediastinal lymphadenopathy
 thymic mass
 germ cell neoplasm
 mediastinal vascular abnormality
 mediastinal neurofibromatosis

27. Mediastinal Masses

28. Approach to a mediastinal mass
Localize to mediastinum
Localize within the mediastinum
Characterise with CT or MRI

29. A. Localize to the mediastinum
• Characteristics indicate that a lesion originates
within the mediastinum:
– Unlike lung lesions, a mediastinal mass will not
contain air bronchograms.
– The margins with the lung will be obtuse. (A lung
mass abutts the mediastinal surface and creates acute
angles with the lung)
– Mediastinal lines (azygoesophageal recess, anterior
and posterior junction lines) will be disrupted.
– There can be associated spinal, costal or sternal
abnormalities.

30. • CXR showing sign of lung mass and mediastinal mass

31. B. Localize within the mediastinum
• The mediastinum can be divided into anterior,
middle and posterior compartments.
• It is important to remember that there is no
tissue plane separating these compartments.

32. Anterior mediastinum
• The anterior mediastinum contains: thymus, lymph nodes,
ascending aorta, pulmonary artery, phrenic nerves and
thyroid.
• The most common lesions seen in the anterior mediastinum will
either be of thymic or lymph node origin.
Even the germ cell tumors arise from the pluripotent cells of the
thymus.
Before we want to biopsy an anterior mediastinal mass, do not
forget that some of these lesions can be vascular in origin.
• The four T's make up the mnemonic for anterior mediastinal
masses::
– Thymus
– Teratoma (germ cell)
– Thyroid
– Terrible Lymphoma

34. • On conventional radiographs look for the signs listed in the
table above
• The finding of an obliterated retrosternal clear space is not so
helpfull anymore, since nowadays many patients are obese. In
these patients the retrosternal space can be filled with fat.

35. Hilum overlay sign
• When there is a mediastinal mass and we still
can see the hilar vessels through the mass, then
we know the mass does not arise from the
hilum. This is known as the hilum overlay
sign.
• Because of the geometry of the mediastinum
most of these masses will be located in the
anterior mediastinum.

36. • Hilum overlay sign in a patient with
lymphoma
Hilum overlay sign in a patient with lymphoma: (a)PA CXR clearly depicts the hila
(white arrow), which indicates that the mass is either anterior or posterior to the
hila. In addition, the descending aorta is clearly seen (black arrow), indicating that
the mass is not within the posterior mediastinum. (b) Chest CT scan
demonstrates an anterior mediastinal mass. The anterior junction line is
obliterated

37. Mediastinal mass (Diagnosed as Hodgkins lymphoma): Wide upper
mediastinum (arrowheads)
Poorly defined aortic knuckle - indicating adjacent disease Wide right
paratracheal stripe (*) Normal lungs

38. Axial CT image showing homogenously enhancing soft tissue anterior
mediastinal mass (arrow) replacing the thymus in a case of thymic
lymphoma.

39. Anterior junction line
• Anterior mediastinal masses in the prevascular
region can obliterate the anterior junction line,
although it is usually the preservation of
more posterior lines at radiography that
helps identify the location of an anterior
mediastinal mass.

40. • Obliteration of cardiophrenic angle by Epicardial fat pad.
• (a) Posteroanterior chest radiograph shows loss of the cardiac
silhouette at the border of the right side of the heart and an
epicardial fat pad with relatively low density (arrow).
• (b) CT scan shows the fat pad (arrow) as an area of homogeneous fat
attenuation adjacent to the right border of the heart.

41. Middle mediastinum
• The middle mediastinum contains: lymph nodes, trachea,
esophagus, azygos vein, vena cavae, posterior heart and the
aortic arch.
• The majority of middle mediastinal masses will consist of foregut
duplication cysts (eg oesophageal duplication or bronchogenic
cysts) or lymphadenopathy.
• Aortic arch anomalies can also present as middle mediastinal
masses.
• Fluid containing lesions are usually duplication cysts or necrotic
lymph nodes.
• A pancreatic fluid collection due to pancreatitis may also present as
a mediastinal mass.
• A fibrovascular esophageal polyp is a mesenchymal lesion which
almost always contains fat.
• Vascular lesions are arch anomalies, azygous continuation due to
interrupted inferior vena cava or hyperenhancing lymph nodes.

43. • Displaced azygoesophageal recess will be seen on the right.
• On the left we may have a pseudoparavertebral line.
This is a new interface that looks like a paravertebral line.

44. • Lymphadenopathy. (a) On CXR PA view , the right paratracheal
stripe is not seen, having been obliterated by a right paratracheal
mass (arrowheads). (b) CT scan demonstrates right paratracheal
lymphadenopathy (arrow), which obliterates the air–soft tissue
interface between the right lung and the tracheal wall.

45. AP window lymphadenopathy. (a) Chest radiograph shows the AP window
with an abnormal convex border (arrow). (b) CT scan demonstrates
lymphadenopathy (arrow), which accounts for the distortion of the AP
window in a.

46. •(a) PA CXR demonstrates a subcarinal abnormality with increased opacity (*),
splaying of the carina, and abnormal convexity of the upper and middle thirds of the
azygoesophageal line (arrowheads).
•(b) Corresponding CT scan helps confirm a subcarinal mass (arrow), which proved
to be a bronchogenic cyst.

47. Pitfalls in assessment of middle mediastinum:
• A variety of normal vascular variants may be mistaken for
middle mediastinal disease at CXR.
• Right-sided aortic arch may mimic paratracheal
lymphadenopathy because it obliterates the right
paratracheal stripe
– the absence of the aortic knuckle on the left should help correctly
identify this variant.
• Left sided SVC may create an additional mediastinal
line lateral to the aortic arch at radiography.
• Azygos continuation of the IVC - provides an alternate
route for systemic venous return to the heart.
– results in an enlarged azygos vein, which may be mistaken for
lymphadenopathy.

48. • Right-sided aortic arch. (a) Posteroanterior chest radiograph demonstrates an
abnormality in the right paratracheal region (arrow) with loss of the paratracheal
stripe. Note, however, the absence of the aortic knuckle on the left. (b) CT scan
shows a right-sided aortic arch (arrow), which explains the findings in a.

49. Left-sided SVC. (a) Collimated PA CXR shows an additional line (arrow)
lateral to the aortic arch. (b) Venogram demonstrates a left-sided SVC,
which explains the finding in a. (c, d) CT scans obtained at the levels of the
aortic arch (c) and pulmonary trunk (d) show the left-sided SVC (arrow),
which drains into the coronary sinus.

50. Azygos continuation of the IVC. (a) Collimated posteroanterior chest
radiograph shows enlargement of the azygos vein at the inferior margin of the
right paratracheal stripe (arrowheads), a finding that mimics lymphadenopathy.
(b) CT scan also shows enlargement of the azygos vein (arrow). This finding
is the result of azygos continuation of the IVC.

51. Posterior mediastinum
• The posterior mediastinum contains: sympathetic ganglia, nerve
roots, lymph nodes, parasympathetic chain, thoracic duct,
descending thoracic aorta, small vessels and the vertebrae.
• Most masses in the posterior mediastinum are neurogenic in
nature. These can arise from the sympathetic ganglia (eg
neuroblastoma) or from the nerve roots (eg schwannoma or
neurofibroma).
• Others masses are: lymphadenopathy, the vertebrae , paravertebral
lesions, and the descending thoracic aorta as potential causes for
posterior mediastinal masses.
• Cystic lesions will be either neuroenteric cysts, schwannomas or
meningoceles.
• Fat containing lesions will be extramedullary hematopoiesis.
When the anemia is resolved the extramedullary marrow will stop
producing blood and become fatty. It appears as a lobulated
paravertebral soft tissue mass behind heart.

52. • On conventional radiographs look for:
– Cervicothoracic Sign
– Widening of the paravertebral stripes
– Displacement of posterior junctional line.

53. a. Radiologic Findings PA chest radiograph demonstrates a well-defined 5.0 cm
homogenous, non-calcified mass in the left apex. The lesion demonstrates a distinct lateral
border but an incomplete medial border. The “incomplete border” sign suggests the lesion is
pleural or mediastinal based. On closer inspection, one notes the lesion extends above the
ipsilateral clavicle, thus exhibiting a “cervicothoracic” sign. This sign localizes the lesion to
the posterior mediastinal compartment. B. On the left the MR of the same patient.
It turned out to be a schwannoma.

54. Paraspinal abscess. (a) Posteroanterior chest radiograph shows a mass
(arrow) effacing the left paraspinal line. The lateral wall of the descending aorta is
seen as a separate entity (arrowhead). (b) CT scan shows a paraspinal abscess
(arrow) effacing the paraspinal lines. The air– soft tissue interface between the
lung and aorta remains intact (arrowhead), thereby preserving the normal
radiographic appearance of the lateral aortic wall (cf a).

55. Descending aortic aneurysm. (a) Posteroanterior chest radiograph
shows lateral displacement of the lateral margin of the descending
thoracic aorta due to an aortic aneurysm (arrowheads). (b) CT scan also
demonstrates the aneurysm (arrow).

56. More than one compartment
• Since there are no tissue planes separating the
mediastinal compartments, there are lesions that do not
respect our approach to the mediastinum.
These lesions tend to occupy more than one
compartment and include: mediastinitis, hematomas,
vascular entities, bronchogenic cancer, metastases
and lymphangiomas (fluid containing).

57. C. Characterize
• Once we have localized a mediastinal mass,
next try to charcterize it by assessing whether
it has any of the following characteristics:
– Does the mass contain fluid?
– Does it contain fat?
– Does it contain calcification?
– Does it enhance following the administration of
intravenous contrast?

58. Fluid
• mediastinal masses that may contain fluid:
– Thymic Cyst
– Thymoma
– Teratoma
– Pericardial Cyst
– Foregut Duplication
– Meningocoele
– Neuroenteric Cyst
– Cystic Lymphadenopathy
– Lymphangioma

59. mass containing fluid: teratoma (on the left) or a thymic cyst (on the right).

60. • B.
a. multiple masses in both the anterior and middle mediastinum. The
attenuation values are of water density. These findings favor the diagnosis of
cystic lymphadenopathy in a patient with metastatic disease.
b. cystic lesion in the middle mediastinum with fluid fluid level and milk of
calcium. Foregut duplication cysts occasionally contain milk of calcium like in
this example of an esophageal duplication cyst.

61. Fat
• Fat on chest film often look like water density, thus
sometime it is difficult to differentiate them
– When fat is inflamed
– When involved with malignant tumor – cellular infiltrate has
water density
• When fat is identified in thoracic lesion
– Teratoma
– Lipoma
– Thymolipoma
– Omental Fat pad
– all hernia
– Excess fat secondary to steroid therapy
– hibernoma

62. Calcification
• Commonly present in the mediastinal lesions
• If within the mass and doesn’t shift with gravity, likely solid
tumor.
• Calcification in margin of mass – usually cyst
– Solid thymoma or substernal thyroid may show rim calcification
• Calcification within a tumor – usually benign
– Thyroid carcinoma and neurosarcoma may show annular or
stippled calcification
• Thymoma with calcifications – myasthenia gravis usually.
• Tooth or bone – teratoma
• Phleboliths - hemangioma

63. Enhancing mass
• The differential diagnosis of enhancing
mediastinal masses is:
– Hyperenhancing lymph nodes
– Thyroid tissue
– Paragangliomas
– Hemangiomas
– Vascular lesions

64. • Enhancing lymph
nodes seen in:
– Melanoma
– Renal cell
carcinoma
– Thyroid
carcinoma
– Castlemann's
disease

65. Air
• Gas within a mediastinal mass
– Hernia
– Esophageal diverticulum
– Dilated esophagus
– Mediastinal abscess
– Communicating duplicating cyst
• Diffuse pneumomediastinum – sources:
– Esophagus, trachea, or bronchus (perforation or surgery)
– Retroperitoneal space (diagnostic pneumoretroperitoneum,
duodenal or colon perforation)
– Neck (trauma, surgery or perforating cervical lesion)
– Lung (parenchymal tear leaks air into interstitium, then dissect to
hilum and into mediastinum)

66. Chest radiography showed perihilar opacities in both lungs with free air in the
mediastinum (image A, arrows). Computed tomography confirmed
pneumomediastinum (image B, arrows) with enhanced interstitial markings and
lower-lobe opacities in both lungs, with greater severity in the left lung

67. Configuration
• True, lymph node enlargement – often lobulated
• Long vertical diameter with undulating margins
– Dilated esophagus
– Dissecting aneurysm
– Azygous vein enlargement
– Mediastinal hematoma
• Teardrop shadow, broad along the diaphragm –
soft pedunculated mass (pericardial cyst or
thymolipoma)
• The third mogul – bumps on heart just below the
pulmonary arc on the left border

68. Mediastinal vs pulmonary lesions
• Sharply penciled margin
• Tapering upper and lower margins
• Involvement of spine or adjacent ribs or even
sternum
• Bilaterality usu. excludes pulmonary lesion
• Respiratory motion: intrapulmonary shadows
move synchronously with the adjacent lung
markings, whereas mediastinal lesions donot.
• Presence of air bronchogram within the lesion –
pulmonary lesion

69. Mediastinal vs cardiac disease
• Hilum overlay vs hilum convergence signs
• Fallacies:
– Certain CHD, especially among infants, may result in
lateral bulge anterior to the pulmonary trunk
– Collapse of left lower lobe may also displace the first left
pulmonary bifurcation posteromedial to its normal position
– Rarely, pericardial effusion may bulge anterolaterally in
front of right and left main pulmonary arteries.
• Absence of pulsation signifies non-cardial origin
– But, transmitted pulsation may be + in pericaridal effusion
and tumor

70. Thyroid mass
• Enlargement of the thyroid gland can be due to a number of causes
including a non-toxic multinodular enlargement of the gland,
Thyrotoxicosis, thyroid adenoma, thyroid carcinoma, lymphoma
and Hashimoto's thyroiditis.
• Less than 5% of enlarged thyroid glands in the neck extend into the
mediastinum to produce a retrosternal goitre, but this is usually
due to a non-toxic multinodular enlargement of the gland.
• A retrosternal goitre appears as a well-defined round or oval soft
tissue mass in the superior part of the anterior or middle
mediastinum, which fades off into the neck. The soft-tissue mass
often contains central nodular, linear or eccentric patterns of
calcification and produces lateral displacement and compression
of the trachea in the thoracic inlet .
• About 25 % of goitres are retrotaeheal and displace the oesophagus
posteriorly and the trachea anteriorly.
• Rapid increase in the size of the mass indicates internal
haemorrhage into a cyst.

71. • Traditionally, the term substernal goitre has been used to
refer to an enlarged thyroid gland with greater than 50% of
its mass below the thoracic inlet. It is of clinical
significance because its growth between the sternum
anteriorly and vertebral bodies posteriorly leads to
impingment on the surrounding structures and has
compressive symptoms.
• This condition has a clinical importance because it presents
a diagnostic dilemma with its compressive symptoms and
operative difficulty as to which approach is most suitable
for its management.
• The CT scan was the most useful tool showing the nature
and extent of the lesion in the reported case.
• Has a higher attenuation level than soft tissue on non contrst
CT due to its iodine content.

72. • (A) The representative chest radiograph; and
(B) chest CT scan of a giant substernal goiter.

73. • Right-sided retrosternal goiter. (a) Posteroanterior chest radiograph demonstrates a thyroid
goiter (arrow) extending into the middle mediastinum, obliterating the right paratracheal stripe, and
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. (b) CT scan shows the mass (arrow) between the trachea and right
lung, a location that explains the obliteration of the right paratracheal stripe seen in a. There is no
contact between the anterior component of the mass and the lung (arrowhead) at the level of the
clavicular heads, a relationship that continues above the level of the clavicles. This finding explains
why the lateral border of the anterior mediastinal component above the level of the clavicles is not
sharp in a.

74. Thymic mass
• Normal thymus – commonest cause of
mediastinal abnormality in infants, seen as
triangular soft tissue mass (sail shadow)
projecting to one side of mediastinum, usually
the right side.
• Thymic wave sign – due to slight indentation
by internal protrusions of the
osteocartilaginous jxns of the adjacent ribs to
the soft normal thymus.

75. Enlargement of thymus
• Thymoma
• Thymic hyperplasia
• Thymic carcinoma
• Lymphoma
• Carcinoid
• Germ cell tumor
• Thymic cyst
• thymolipoma
• Thymoma – commonest
thymic tumor in adult
– 30% are invasive or
malignant
– 10-15% with MG –
thymoma
– 25-50% with thymoma –
MG
– May contain curvilinear or
nodular calcification
– Presence of vascular
encasement or pleural
metastasis – invasive
thymoma

76. • Radiograph: well defined round or
oval soft tissue mass projecting to
one side of anterior mediastinum
when large.
• Thymolipoma: very large soft
tissue mas with less radiographic
density than expected for its size.
• CT: well defined mass of soft tissue
atttenuation in anterior mediastinum
• May contain areas of cystic
degeneration
• Normal shaped enlarged thymus –
hyperplasia
• Cystic thymic mass
• Fat containing - thymolipoma

77. • Thymic Hyperplasia. A. Enhanced CT in a 12-year-old undergoing
chemotherapy for rhabdomyosarcoma shows virtual absence of
thymic tissue. B. Scan 3 months following completion of
chemotherapy shows uniform enlargement of thymus (arrow),
reflecting rebound hyperplasia.

78. Thymic enlargement on (A) PA and (B) lateral radiographs of a patient with a
malignant thymic mass. The lateral view demonstrates pleural metastases
posteriorly (arrows). (C) CT confirms the anterior position of the primary tumour
suspected from the filling of the retrosternal window apparent on the lateral
radiograph (B).

79. Invasive thymoma in a young man. (A) Shows a lobular anterior mediastinal
mass associated with a pleural effusion. (B) Image obtained through the
lower chest demonstrates mixed soft tissue (arrows) and fluid attenuation
owing to transpleural spread of tumour.

80. Germ cell tumors
• Majority are benign
– Dermoid cyst
– Benign teratoma
• 30% are malignant
– Seminoma
– Embryonal cell carcinoma
– Choriocarcinoma
– Endodermal sinus or yolk sac
tumor
• Dermoid – mainly of
ectodermal tissues
• Teratoma – ectodermal,
mesodermal and endodermal
origin tissues
• Usually incidental anterior
mediastinal soft tissue mass in
young adult male
• Benign – well defined round or
oval, usually projecting to only
one side of anterior
mediastinum
• Malignant – lobulated, usually
projecting on both sides of
mediastinum
• May contain – peripheral rim
or central nodular
calcifications, fat-fluid level,
rudimentary tooth, hair tufts
• Rapid increase in size –
internal hemorrhage or
development of malignancy.

81. • Teratoma in a young man undergoing an immigration chest
radiograph. (A) There are no specific features on the plain
radiograph to indicate the nature of the mass. (B) CT demonstrates
that the opacity visible on the chest radiograph is well defined and
contains soft tissue and fat densities.

82. • Malignant Germ Cell Tumor. A. Posteroanterior chest radiograph in a 38-year-old
man reveals a right mediastinal mass with discrete right lung nodules (arrows). B.
Contrast-enhanced CT demonstrates a large anterior mediastinal mass invading the
superior vena cava (arrow) with right lung nodules and a small pleural effusion. CT-
guided biopsy showed choriocarcinoma.

83. Lymphoma
• A. Posteroanterior chest radiograph in a 35-year-old man
shows a large, lobulated mediastinal mass. B. Contrast-
enhanced CT at the level of the aortic arch shows bulky
anterior and middle mediastinal lymphadenopathy.

84. • Causes:
– Metastatic disease
– Lymphoma
– Leukaemia
– Sarcoidosis
– Tuberculosis
– Histoplasmosis
– Other infections and
inflammatory conditions
• Calcifications:
– Tuberculosis
– Sarcoidosis*
– Silicosis*
– Histoplasmosis
– Hodgkin’s disease
after irradiation
– Metastases from
mucin secreting
adenocarcinoma
– Amyloidosis*
– Castleman’s disease
– P. carinii pneumonia
in AIDS
Enlarged lymph nodes with central
necrosis:
•Tuberculosis
•Histoplasomosis
•M. avium intracellulare
•Hodgkin’s disease
•Metastases (SCC, testicular tumors)
Mediastinal lymphadenopathy

85. Thoracic aortic aneurysm
• Causes:
– Atherosclerosis
– Hypertension
– Blunt chest trauma
– Mycotic dissection
– Cystic medial necrosis in
Marfan’s and E-D syndrome
– Aortitis in 3o syphilis
– Takayasu’s disease
– Congenital (sinus of valsalva
aneurysm, coarctation)
• Appears as either widening
of the mediastinum or as
well defined round or oval
soft-tissue mass in any part
of mediastinum, often with
curvilinear calcification in
its wall
• Calcification in ascending
aorta: syphilis or
atherosclerosis
• Displacement of peripheral
rim of calcification away
from wall - dissection

86. • Mediastinal Hematoma From Ruptured Thoracic Aortic Aneurysm. A. Portable chest radiograph in
an 83-year-old woman with chest pain shows marked mediastinal widening. B. Contrast-enhanced
CT demonstrates aneurysmal dilatation of the descending aorta, with active extravasation (arrow)
into a large mediastinal hematoma. The patient was not a surgical candidate and expired shortly after
the study.

87. Neurogenic tumors
• 3 groups
• 1st: nerve sheath tumors
– Include neurofibroma, schwannoma, neurofibrosarcoma
and malignant schwannoma
– Commonest neurogenic tumor in mediastinum of adults
• 2nd: ganglion cell tumors
– Ganglioneuroma, ganglioneuroblastoma and neuroblastoma
– Commonest neurogenic tumor in mediastinum of children
• 3rd: chemodectoma and phaeochromocytoma
– Rarest
• Majority are benign, 30% are malignant

88. • Well defined round or oval soft tissue mass in
paravertebral gutter, usually projecting on only one side
of the posterior mediastinum
– Nerve sheath tumors – circular
– Ganglion cell tumors – elongated
• Central calcification – may be in ganglion cell tumors
(rare in nerve sheath tumors)
• Radiographs:
– Pressure erosion of adjacent vertebrae, ribs
– Splaying of ribs
– Widening of intervertebral foramen (dumb-bell tumours
leading to compression of spinal cord), rib notching,
scoliosis
• Rapid increase in size with bony destruction and pleural
effusion – development of malignancy

89. • Neurofibroma. A. Frontal chest radiograph shows a left upper mediastinal
mass (arrow). B. Contrast-enhanced CT confirms the presence of a left
paravertebral soft tissue mass (arrow). Surgical resection confirmed a
neurofibroma.

90. • Ganglioneuroma. A. Posteroanterior radiograph in a 15-year-old woman reveals an
oval, vertically oriented, right-sided mediastinal mass (arrows). B. Contrast-
enhanced CT shows a low-attenuation posterior mediastinal mass (arrow) with
calcification. This was surgically proven to be ganglioneuroma.

91. Summary
• The divisions of the mediastinum are not absolute; however,
referring to the local anatomy of the mediastinal reflections in
an attempt to more accurately localize an abnormality may
help narrow the differential diagnosis.
• Identification of the involved mediastinal compartment helps
determine which imaging modality might be appropriate for
further study.
• Different imaging characteristics and extension of the lesion
further helps to narrow down the possible diagnosis or to reach
the final diagnosis of mediastinal pathologies.

92. References:
• Textbook of radiology and imaging by David
Sutton 7th edition
• A Diagnostic Approach to Mediastinal Abnormalities:
RadioGraphicsVol. 27, No. 3 by Whitten CR et al.
https://doi.org/10.1148/rg.273065136
• Radiology assistant

93. THANK YOU !