radiology mediastinum

8/13/2019 Radiology Mediastinum

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Approach to

Mediastinal Masses


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Clinical Presentation:33% of all masses present in patients less than15 years old

If small, usually asymptomatic and foundincidentally (cautious work up)If large, usually present with respiratory distress

(frantic work up)


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-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 andsternum), thymus.

-Therefore will most likely

see masses typical to

these structures, ie a

lymphoma in lymph nodes.


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It is located above a

horizontal line drawn from

the angle of Louis posteriorly

to the spine.

Structures in the superiormediastinal compartment

include the thyroid gland,

aortic arch and great

vessels, proximal portions of

the vagus and recurrent

laryngeal nerves, esophagus

and trachea.
http://www.vh.org/adult/provider/radiology/icmrad/Opening.html


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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 hemiazygousveins.


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Anterior Mediastinal Masses: (4 T's)

(30% of mediastinal masses)

Thymoma

Teratoma

Thyroid (Ectopic) (Terrible) Lymphoma


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Middle Mediastinal Masses (A + B)


Adenopathy (infection [bacterial,granulomatous], neoplasm [leukemia /lymphoma, metastases])

Bronchopulmonary foregut malformations(Esophageal duplication cyst, bronchogenic cyst,sequestration)


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Posterior Mediastinal Masses: (N)


Sympathetic ganglion tumors: neuroblastoma,ganglioneuroblastoma, ganglioneuroma (95% ofposterior mediastinal masses)

Neurofibroma

Neurenteric cyst

Extramedullary hematopoesis Paravertebral soft tissue mass from infection


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Approach/Discussion:

PA and lateral chest films are the first step indistinguishing from which mediastinal compartment themass is arising from.

Computed tomography or magnetic resonance imagingis the next step, better characterizing the nature andextent of the lesion, thus narrowing the differentialdiagnosis. MRI is especially good at looking for spinalcanal invasion in posterior mediastinal masses

Tissue biopsy is required for definitive diagnosis, andsurgical resection for definitive cure.


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Case 37 - Eight year old

male with a heart murmur


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CT exam show a low density

mass in the anterior

mediastinum with irregularwalls with calcium in it.

Dx Teratoma, Anterior

Mediastinal


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Three year old male withan incidentally noted

chest mass


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single slice from an enhanced chest CT exam shows the mass to be non-

enhancing, posterior to the right bronchi, and next to the esophagus.

Dx: Esophageal Duplication


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Eighteen year old femalewith an incidentally noted

chest mass


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Esophageal duplication cyst


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Eleven year old male with

upper respiratory

symptoms and wheezing.


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Slice from an enhanced chest CT exam shows a multi-loculated non enhancing

mass in the anterior mediastinum

Dx-Thymic Cyst


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Five year old male with cough and fever


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Soft tissue in the anterior mediastinum compatible in appearance with thymus


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PA and lateral chest films show a large,

lobulated anterior mediastinal mass

displacing the trachea to the right.

Twelve year old female with a chest mass


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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


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PA and lateral chest films show a mediastinal

mass that had enlarged in the 4 year interval

hat may be spreading the right 5th and 6th

ribs apart.


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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


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PA and lateral chest films show ananterior mediastinal mass and a large

right pleural effusion.


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Two contiguous slices

from an enhanced chest

CT exam show a

homogenous, solid,

anterior mediastinal massand a large right pleural

effusion.

Dx-Lymphoma, Non-

Hodgkin, Anterior

Mediastinal


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PA and lateral chest films show a softtissue mass in the right posterior

costophrenic sulcus.


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PA and lateral chest films from the dayof admission demonstrate a large

round opacity in the left lower lobe that

abuts the diaphragm


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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


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large mass in the posterior

mediastinum on the left.


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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 invasionor liver metastases are seen


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MRI exam performed 3 weeks after

diagnosis. Coronal and sagittal T1

weighted images without contrast, andcoronal 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 neuralforamina and the s inal canal.

Dx-Neuroblastoma


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Germ Cell

. Almost all of them originate in the anterior mediastinum withinor in close contact with the thymus. There is a variety of benignand malignant germ cell neoplasms. The majority of germ cellneoplasms (6070%) are benign including mostly mediastinalteratoma and dermoid cysts that occur with equal frequency in

males and females. On CT scans, the tumour is heterogeneous and limited with

well-defined margins. Dermoid cysts and teratomas contain areasof 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 highlysuggestive of the diagnosis. Curvilinear, spherical or irregularcalcifications within the mass may be seen Identification of atooth, while rare, is diagnostic.


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Lymphoma

primary malignant neoplasm of thelymphoreticular system, particularly of thelymphocytes and histiocytes and the derivatives

of these two cell types, surrounded by non-neoplastic inflammatory cells. Lymphomasinclude Hodgkins diseaseand non Hodgkins

lymphoma. Both frequently involve the chest.
http://www.amershamhealth.com/medcyclopaedia/Volume%20V%201/Hodgkins%20disease.htmlhttp://www.amershamhealth.com/medcyclopaedia/Volume%20V%201/non%20Hodgkins%20lymphoma.htmlhttp://www.amershamhealth.com/medcyclopaedia/Volume%20V%201/non%20Hodgkins%20lymphoma.htmlhttp://www.amershamhealth.com/medcyclopaedia/Volume%20V%201/non%20Hodgkins%20lymphoma.htmlhttp://www.amershamhealth.com/medcyclopaedia/Volume%20V%201/non%20Hodgkins%20lymphoma.htmlhttp://www.amershamhealth.com/medcyclopaedia/Volume%20V%201/Hodgkins%20disease.html


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Thymoma,

neoplasm arising from thymic epithelium. It is the most common cause of a thymic mass. It presents as ananterior mediastinal mass.

Thymomas occur usually between the ages of 40 and 60 years old, in males or females equally. They are veryunusual in patients under the age of 20. Thymomas generally occur as incidental findings discovered on a chestradiograph in otherwise healthy individuals. They may also occur in association with other abnormalities suchas myasthenia gravis, red cell aplasia and hypogammaglobulinaemia. Myasthenia gravis, the most frequentassociation of the three, is present in roughly 50% of patients with thymoma. Approximately 15% of patientswith myasthenia gravis have a thymoma

On the chest radiograph, thymomas are depicted as a round or lobulated mass located in the anteriormediastinum

. 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 andoccasionally as low as the cardiophrenic angle.

Occasionally the tumour is too small (1 cm) to be depicted on the chest radiograph, and is onlydetected on CT scans Punctuate or curvilinear calcifications may be seen in both benign or invasivethymomas.

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 anteriormediastinum. Intratumoral calcifications are present in 20 30% of the cases and areas of cysticdegeneration are common

Invasive thymomas typically appear as irregular masses growing along pleural surfaces.


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Bronchogenic cysts

On the chest radiograph, bronchogenic cysts typically appear as smooth,sharply marginated mediastinal masses. On CT scans they appear as round oroval homogeneous masses with well-defined margins with barely or noperceptible walls. They have a certain plasticity and mould around normalanatomical structures (Fig.1). Half of them show an attenuation similar to thatof 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 enhancementafter administration of iodinated contrast medium is the rule.

On MR scans, bronchogenic cysts frequently show a signal intensity higherthan that of muscle on T1-weighted images due to their high proteinaceouscontent (Fig. 1b). Uncommonly a fluidfluid level may be present. The signalintensity on T2-weighted images is very high suggesting a cystic lesion (Fig.1c). The absence of enhancement after intravenous injection of gadoliniumallows differentiation of the cysts from solid tumours


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LAD

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 rightupper paratracheal nodes causes uniform or lobular widening of the right paratracheal stripe, andan increase in density of the superior vena cava of which the border may become convex to thelung. The enlarged right lower paratracheal nodes push the azygos vein laterally increasing thediameter 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 mainpulmonary artery. If they are substantially enlarged, the left upper paratracheal nodes inducemediastinal 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 onthe posteroanterior film and a lack of visibility of the external surface of the medial wall of theintermediate 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. Increasedopacity of the retrosternal area on the lateral view may be sometimes the early sign. Enlarged paraoesophageal and posterior mediastinal nodes produce displacement of the azygo-

oesophageal and paraspinal lines. The radiographic signs of enlargement of hilar lymph nodes arehilar enlargement, lobulation of outline or rounded mass in a portion of the hilum
http://www.amershamhealth.com/medcyclopaedia/Volume%20V%201/lymph%20node%20classification%20chest.htmlhttp://www.amershamhealth.com/medcyclopaedia/Volume%20V%201/lymph%20node%20classification%20chest.html


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LAD

CT 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 nodesare normal or abnormal (lung cancer staging). The larger the node, the more likely it indicates a significantabnormality. 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 knowndisease an enlarged node less than 2 cm in short axis diameter should be regarded as likely to be hyperplastic orpostinflammatory. 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 oflymphadenopathy whereas coalescence of enlarged nodes suggests infections, granulomatous disease andneoplasm. Diffuse mediastinal involvement is more typical of lymphoma, large cell undifferentiated carcinomaand acute or chronic mediastinitis. CT can also be used to define the density of lymph nodes. Enlarged nodesmay be calcified (see calcification mediastinal lymph node), or low in density and necrotic in appearance or canenhance following intravenous injection of contrast media. Low attenuation lymph nodes after administrationof contrast media, with or without rim enhancement typically reflect the presence of necrosis
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Pericardial cyst,

The majority of them are located in the right anterior cardiophrenic anglealthough they may occur anywhere in the pericardium, posteriorcardiophrenic angle or superior retroaortic pericardial recess.

On chest radiographs, they appear as well defined round or oval masses incontact 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 wateror, because of viscous fluid, may be in the soft tissue range

Similarly the MR signal characteristics are typically that of water (low signalintensity 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.


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Extramedullary haematopoiesis,

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 homogeneousmass of soft tissue or slightly higher density structure


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Neuroenteric cyst, mediastinal,

The vertebral anomalies including hemivertebrae,butterfly vertebra or spina bifida may be located at thelevel 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 masseslocated in the posterior mediastinum or paravertebralarea.

Their communication with the subarachnoid spacesmay be demonstrated on MR scans, which havereplaced CT myelography.


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Neurogenic tumours

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 andfemales are equally affected.

On chest radiography, neurogenic neoplasms are seen as a sharplycircumscribed homogeneous mass (Fig.1). Rib erosion with a sclerotic borderis suggestive of a benign lesion. The presence of frank bone destruction or

spread to multiple ribs is suggestive of malignancy. Calcification may bepresent 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 thelipid elements in the nerve sheaths or cystic degeneration. Due to theirvascularization, they enhance after the administration of intravenous contrast

medium.


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homogeneou

s mass

abutting theright border

of the heart

which

corresponds

to a

schwannomaof the right

phrenic

nerve.


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CT is recommended as the primary imaging modality for assessing masseslocalized within the anterior and middle compartments of the mediastinum. Itprovides information on the precise location of the mass and its relationshipto 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 vascularinvasion.

For masses localized in the posterior compartment of the mediastinum, MRI

is preferentially used because of its superior ability in assessing therelationship of the mass to the adjacent spine. In case of suspicion ofoesophageal abnormality, a barium swallow is indicated.

radiology mediastinum

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