Download Approach to Mediastinal Masses

Approach to
Mediastinal Masses
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Clinical Presentation:
33% of all masses present in patients less than
15 years old
If small, usually asymptomatic and found
incidentally (cautious work up)
If large, usually present with respiratory distress
(frantic work up)
-The anterior mediastinal
compartment is bordered
by the sternum anteriorly,
and the ventral cardiac
surface posteriorly.
-This compartment
contains fat, ascending
aorta, lymph nodes,
internal mammary artery
and vein, adjacent osseous
structures (ribs and
sternum), thymus.
-Therefore will most likely
see masses typical to
these structures, ie a
lymphoma in lymph nodes.
It is located above a
horizontal line drawn from
the angle of Louis posteriorly
to the spine.
Structures in the superior
mediastinal compartment
include the thyroid gland,
aortic arch and great
vessels, proximal portions of
the vagus and recurrent
laryngeal nerves, esophagus
and trachea.
The borders are
composed of the anterior
mediastinal compartment
ventrally, and the anterior
surface of the spine,
posteriorly.
Structures in the middle
mediastinal compartment
include the esophagus
(which will not be visible
unless there is a problem),
vagus nerve, recurrent
laryngeal nerve, heart,
proximal pulmonary
arteries and veins (hilar),
trachea and root of the
bronchial tree, and
superior and inferior vena
cava
The posterior mediastinum borders
the anterior surface of the spine
posteriorly to the ribs.
Structures in the posterior
mediastinal compartment include
the descending aorta, adjacent
osseous structures (the spine and
ribs) and nerves, roots, spinal cord,
and the azygous and hemiazygous
veins.
Anterior Mediastinal Masses: (4 T's)
(30% of mediastinal masses)
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Thymoma
Teratoma
Thyroid (Ectopic)
(Terrible) Lymphoma
Middle Mediastinal Masses (A + B)
(30% of mediastinal masses)
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Adenopathy (infection [bacterial,
granulomatous], neoplasm [leukemia /
lymphoma, metastases])
Bronchopulmonary foregut malformations
(Esophageal duplication cyst, bronchogenic cyst,
sequestration)
Posterior Mediastinal Masses: (N)
(40% of mediastinal masses)
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Sympathetic ganglion tumors: neuroblastoma,
ganglioneuroblastoma, ganglioneuroma (95% of
posterior mediastinal masses)
Neurofibroma
Neurenteric cyst
Extramedullary hematopoesis
Paravertebral soft tissue mass from infection
Approach/Discussion:
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PA and lateral chest films are the first step in
distinguishing from which mediastinal compartment the
mass is arising from.
Computed tomography or magnetic resonance imaging
is the next step, better characterizing the nature and
extent of the lesion, thus narrowing the differential
diagnosis. MRI is especially good at looking for spinal
canal invasion in posterior mediastinal masses
Tissue biopsy is required for definitive diagnosis, and
surgical resection for definitive cure.
Case 37 - Eight year old
male with a heart
murmur
PA and lateral chest films show a
large anterior mediastinal mass
causing narrowing and rightward
deviation of the trachea. The mass
is not calcified.
CT exam show a low density
mass in the anterior
mediastinum with irregular
walls with calcium in it.
Dx Teratoma, Anterior
Mediastinal
Three year old male with
an incidentally noted
chest mass
single slice from an enhanced chest CT exam shows the mass to be nonenhancing, posterior to the right bronchi, and next to the esophagus.
Dx: Esophageal Duplication
Eighteen year old female
with an incidentally noted
chest mass
Esophageal duplication cyst
Eleven year old male with
upper respiratory
symptoms and wheezing.
Slice from an enhanced chest CT exam shows a multi-loculated non enhancing
mass in the anterior mediastinum
Dx-Thymic Cyst
Five year old male with cough and fever
Soft tissue in the anterior mediastinum compatible in appearance with thymus
Twelve year old female with a chest mass
PA and lateral chest films show a large,
lobulated anterior mediastinal mass
displacing the trachea to the right.
A chest CT exam shows the mass to extend from the neck to the diaphragm,
compressing the tracheal and left mainstem bronchus leading to left lower lobe
atelectasis. The chest wall mass is partially eroding the sternum and there is
periosteal reaction. Axillary adenopathy is present also.
Dx:Lymphoma, Hodgkin, Anterior Mediastinal, Sternal Involvement
PA and lateral chest films show a mediastinal
mass that had enlarged in the 4 year interval
that may be spreading the right 5th and 6th
ribs apart.
An enhanced chest CT exam shows a homogeneous mass, of fatty density, with a few
septations, in the right posterior mediastinum causing some anterior displacement of
the right mainstem bronchus.
Dx:Lipoma, Posterior Mediastinal
PA and lateral chest films show an
anterior mediastinal mass and a large
right pleural effusion.
Two contiguous slices
from an enhanced chest
CT exam show a
homogenous, solid,
anterior mediastinal mass
and a large right pleural
effusion.
Dx-Lymphoma, NonHodgkin, Anterior
Mediastinal
PA and lateral chest films show a soft
tissue mass in the right posterior
costophrenic sulcus.
Final Diagnosis:
Intrathoracic Kidney
PA and lateral chest films from the day
of admission demonstrate a large
round opacity in the left lower lobe that
abuts the diaphragm
Two coronal T1 weighted images and one axial T2 weighted image from an MRI
exam from the 5th hospital day demonstrate a posterior mediastinal mass that
extends into the retrocrural regions of the chest bilaterally and that enhances
uniformly. There is no evidence of metastatic disease.
Dx-Sequestration, Extralobar
large mass in the posterior
mediastinum on the left.
Bone window images from a chest CT exam from the day of diagnosis demonstrate a
large spherical calcified left paravertebral mass measuring 12 x 11 x 8 cm in size. There
is a pleural effusion and a shift of mediastinal structures to the right. The mass appears
to extend via the retrocrural space into the abdomen causing displacement of the left
kidney and inferior vena cava. The mass crosses the midline. Some minimal thoracic
vertebral body remodeling and rib thinning is seen on the left. No spinal canal invasion
or liver metastases are seen
Dx-Neuroblastoma
MRI exam performed 3 weeks after
diagnosis. Coronal and sagittal T1
weighted images without contrast, and
coronal and axial T2 weighted MRI
images could not definitely identify the
left adrenal gland, and therefore
suggested it could be the origin of the
midline mass. There was evidence of
tumor invasion into several neural
foramina and the spinal canal.
Germ Cell
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. Almost all of them originate in the anterior mediastinum within
or in close contact with the thymus. There is a variety of benign
and malignant germ cell neoplasms. The majority of germ cell
neoplasms (60–70%) are benign including mostly mediastinal
teratoma and dermoid cysts that occur with equal frequency in
males and females.
On CT scans, the tumour is heterogeneous and limited with welldefined margins. Dermoid cysts and teratomas contain areas of
different densities including fat, soft tissue and cystic
Fatty and cystic components are present in about half of the
cases. Occasionally a fat–fluid level may be present and is highly
suggestive of the diagnosis. Curvilinear, spherical or irregular
calcifications within the mass may be seen Identification of a
tooth, while rare, is diagnostic.
Germ Cell Tumors
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Malignant germ-cell neoplasms have a male predominance. They include
mediastinal seminoma, mediastinal choriocarcinoma, embryonal cell
carcinoma, yolk sac tumour and teratocarcinomas
On the radiograph, the mass is similar to benign germ cell neoplasm excepted
that the mass itself is often lobular in outline. Metastases may be seen in the
lung, pleura or bone. CT or MR features of the tumour are similar to other
primary malignant tumours arising within the anterior mediastinum
The mass is lobular and asymmetrical. The margins may be well-defined or
irregular. The adjacent mediastinal fat planes may be obliterated, although this
is not a feature of definite invasion. The tumour may appear as either a
homogeneous soft tissue mass or a heterogeneous mass containing areas of
contrast enhancement interspersed with areas of decreased attenuation due to
necrosis or haemorrhage
Calcifications are uncommon.
Mediastinal lymphadenopathy may be present
Lymphoma
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primary malignant neoplasm of the
lymphoreticular system, particularly of the
lymphocytes and histiocytes and the derivatives
of these two cell types, surrounded by nonneoplastic inflammatory cells. Lymphomas
include Hodgkins disease and non Hodgkins
lymphoma. Both frequently involve the chest.
Thymoma,
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neoplasm arising from thymic epithelium. It is the most common cause of a thymic mass. It presents as an
anterior mediastinal mass.
Thymomas occur usually between the ages of 40 and 60 years old, in males or females equally. They are very
unusual in patients under the age of 20. Thymomas generally occur as incidental findings discovered on a chest
radiograph in otherwise healthy individuals. They may also occur in association with other abnormalities such
as myasthenia gravis, red cell aplasia and hypogammaglobulinaemia. Myasthenia gravis, the most frequent
association of the three, is present in roughly 50% of patients with thymoma. Approximately 15% of patients
with myasthenia gravis have a thymoma
On the chest radiograph, thymomas are depicted as a round or lobulated mass located in the anterior
mediastinum
. On lateral films, they often appear as a well-defined mass in the normally clear restrosternal space.
Sometimes, the tumour is situated more inferiorly adjacent to the left or right borders of the heart and
occasionally as low as the cardiophrenic angle.
Occasionally the tumour is too small (1 cm) to be depicted on the chest radiograph, and is only
detected on CT scans Punctuate or curvilinear calcifications may be seen in both benign or invasive
thymomas.
On CT scans, benign thymomas appear as a round or oval mass located in the prevascular space of
the mediastinum, or at any level from the thoracic inlet to the diaphragm within the anterior
mediastinum. Intratumoral calcifications are present in 20 – 30% of the cases and areas of cystic
degeneration are common
Invasive thymomas typically appear as irregular masses growing along pleural surfaces.
Thymic cyst,
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may be congenital or acquired.
On plain radiographs, thymic cysts are indistinguishable
from other nonlobulated thymic masses, notably
thymomas
CT scans show a well-defined cystic mass
demonstrating CT attenuation values typically
consistent with fluid. The appearance, however, may
vary if haemorrhage or infection complicate the cyst.
Curvilinear calcification of the cyst wall may occur in a
few cases.
Thyroid mass, mediastinal,
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usually a colloid or adenomatous goitre, and occasionally a carcinoma.
The great majority of mediastinal thyroid masses represent a downward extension of a thyroid mass that
originates in the neck. They may extend into the anterior, middle and posterior compartments of the
mediastinum. When located in the anterior mediastinum, thyroid masses are almost always located posterior to
the great vessels, most often in a paratracheal location. A true primary ectopic mediastinal goitre is very rare.
Most patients are asymptomatic; symptoms, however, may arise from compression of the trachea and
oesophagus.
On chest radiographs, intrathoracic thyroid masses have a well-defined spherical or lobular outline.
They may displace and narrow the trachea. Posteriorly placed thyroid masses separate normal trachea
and the oesophagus. Occasionally they may compress the brachiocephalic veins and cause superior
vena cava obstruction. On CT scans the mediastinal mass due to thyroid goitre typically contains:
- foci of high attenuation on enhanced scans reflecting the high iodine content of thyroid tissue;
- foci of calcifications (usually dense and well defined, with a nodular, curvilinear or circular
configuration); and
- intense and prolonged enhancement following intravenous contrast The key feature for the
diagnosis is demonstration of continuity of the mass with the cervical thyroid gland. This is easily
obtained by helical CT scan over the lower neck and chest. Chest MR may also be used. Radioiodine
scan may also onfirm the diagnosis by demonstration of radioiodine uptake from foci of functional
thyroid tissue within the mass. Distinction between benign and malignant goitre by imaging is not
possible unless the tumour clearly invades the adjacent structures.
Bronchogenic cysts
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On the chest radiograph, bronchogenic cysts typically appear as smooth,
sharply marginated mediastinal masses. On CT scans they appear as round or
oval homogeneous masses with well-defined margins with barely or no
perceptible walls. They have a certain plasticity and mould around normal
anatomical structures (Fig.1). Half of them show an attenuation similar to
that of water and the remainder appear of soft tissue attenuation.
Occasionally they show a very high attenuation related to a milk of calcium
content. Curvilinear calcification of the wall is very rare. Absence of
enhancement after administration of iodinated contrast medium is the rule.
On MR scans, bronchogenic cysts frequently show a signal intensity higher
than that of muscle on T1-weighted images due to their high proteinaceous
content (Fig. 1b). Uncommonly a fluid–fluid level may be present. The signal
intensity on T2-weighted images is very high suggesting a cystic lesion (Fig.
1c). The absence of enhancement after intravenous injection of gadolinium
allows differentiation of the cysts from solid tumours
LAD
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Chest radiograph
On the chest radiograph, the ease with which lymph node enlargement can be recognized
depends on the particular location (see lymph node classification chest). Enlargement of the right
upper paratracheal nodes causes uniform or lobular widening of the right paratracheal stripe, and
an increase in density of the superior vena cava of which the border may become convex to the
lung. The enlarged right lower paratracheal nodes push the azygos vein laterally increasing the
diameter of the combined opacities of both node and azygos arch
The aortopulmonary nodes may cause a bulge in the angle between the aortic arch and the main
pulmonary artery. If they are substantially enlarged, the left upper paratracheal nodes induce
mediastinal widening.
The radiographic features of subcarinal node enlargement include the displacement of the
azygo-oesophageal line that becomes convex to the lung, an increased opacity of the subcarinal
space on the posteroanterior film and a lack of visibility of the external surface of the medial wall
of the intermediate bronchus.
Enlargement of the anterior mediastinal nodes may be substantial to be visible on the chest films.
In such case, mediastinal widening is frequently bilateral and lobulated in outline. Increased
opacity of the retrosternal area on the lateral view may be sometimes the early sign.
Enlarged paraoesophageal and posterior mediastinal nodes produce displacement of the azygooesophageal and paraspinal lines. The radiographic signs of enlargement of hilar lymph nodes are
hilar enlargement, lobulation of outline or rounded mass in a portion of the hilum
LAD
CT
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Lymph node enlargement is defined on the basis of a short-axis node diameter exceeding 1 cm. The
assessment of lymph node size, however, has a limited accuracy in determining whether hilar and mediastinal
lymph nodes are normal or abnormal (lung cancer staging). The larger the node, the more likely it indicates a
significant abnormality. Lymph nodes having a short axis of 2 cm or more, often reflect the presence of
neoplasm, sarcoidosis or infection and should always be regarded as potentially significant. In the absence of a
known disease an enlarged node less than 2 cm in short axis diameter should be regarded as likely to be
hyperplastic or postinflammatory. Three CT patterns may be identified:
discrete enlarged nodes that remain well defined;
coalescence of enlarged nodes, involving surrounding mediastinal fat and forming a single larger mass with
poor margins that can indicate extension of the disease process through the node capsule; and
diffuse mediastinal involvement characterized by infiltration of mediastinal connective tissue and fat with no
recognizable nodes or node masses. The first pattern may be seen in association with all causes of
lymphadenopathy whereas coalescence of enlarged nodes suggests infections, granulomatous disease and
neoplasm. Diffuse mediastinal involvement is more typical of lymphoma, large cell undifferentiated carcinoma
and acute or chronic mediastinitis. CT can also be used to define the density of lymph nodes. Enlarged nodes
may be calcified (see calcification mediastinal lymph node), or low in density and necrotic in appearance or can
enhance following intravenous injection of contrast media. Low attenuation lymph nodes after administration
of contrast media, with or without rim enhancement typically reflect the presence of necrosis
Pericardial cyst,
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The majority of them are located in the right anterior cardiophrenic angle
although they may occur anywhere in the pericardium, posterior
cardiophrenic angle or superior retroaortic pericardial recess.
On chest radiographs, they appear as well defined round or oval masses in
contact with the heart
Calcification is exceptional.
On CT, they appear as smooth well-defined masses without any perceptible
wall. They typically demonstrate fluid attenuation that may be close to water
or, because of viscous fluid, may be in the soft tissue range
Similarly the MR signal characteristics are typically that of water (low signal
intensity on T1-weighted images, and bright signal on T2- weighted images)
(Fig. 1c, d). but may vary depending on the cyst content. The pericardial cyst
may be of almost any size.
Extramedullary haematopoiesis,
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rare marrow expansion associated with severe anaemia,
notably thalassaemia and sickle cell disease.
It is a rare cause of masslike collections within the
chest. The masses are usually asymptomatic.
Radiologically they present typically as longitudinal,
bilateral, lobulated paraspinal masses
On CT scans the appearance is that of homogeneous
mass of soft tissue or slightly higher density structure
Neuroenteric cyst, mediastinal,
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The vertebral anomalies including hemivertebrae,
butterfly vertebra or spina bifida may be located at the
level of the cyst.
The cyst may be connected to the meninges through a
midline defect in one or more vertebral bodies.
Radiographically, neuroenteric cysts are round, oval or
lobulated well-defined homogeneous cystic masses
located in the posterior mediastinum or paravertebral
area.
Their communication with the subarachnoid spaces
may be demonstrated on MR scans, which have
replaced CT myelography.
Neurogenic tumours
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Roughly 70% of neurogenic tumours arising in the chest are benign. Usually,
they occur in younger patients, in the first four decades of life. Males and
females are equally affected.
On chest radiography, neurogenic neoplasms are seen as a sharply
circumscribed homogeneous mass (Fig.1). Rib erosion with a sclerotic border
is suggestive of a benign lesion. The presence of frank bone destruction or
spread to multiple ribs is suggestive of malignancy. Calcification may be
present in all types of neurogenic neoplasm
On CT scans, neurogenic neoplasms typically appear as homogeneous soft
tissue density although many of them have a low attenuation attributed to the
lipid elements in the nerve sheaths or cystic degeneration. Due to their
vascularization, they enhance after the administration of intravenous contrast
medium.
homogeneou
s mass
abutting the
right border
of the heart
which
corresponds
to a
schwannoma
of the right
phrenic
nerve.
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CT is recommended as the primary imaging modality for assessing masses
localized within the anterior and middle compartments of the mediastinum. It
provides information on the precise location of the mass and its relationship
to adjacent structures. It can determine whether the mass is cystic or solid,
and whether it contains calcium or fat.
Contrast enhancement provides information concerning the vascularization
of the mass and its relationship with adjacent structures.
Radioiodine scan is required if thyroid goitre is suspected.
MRI is superior to contrast enhanced CT, however, in assessing the
relationships of the mass to vascular structures and in determining vascular
invasion.
For masses localized in the posterior compartment of the mediastinum, MRI
is preferentially used because of its superior ability in assessing the
relationship of the mass to the adjacent spine. In case of suspicion of
oesophageal abnormality, a barium swallow is indicated.