Rad Mediastinum FKUnLam

8/13/2019 Rad Mediastinum FKUnLam

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Radiology Examination ofMediastinum

Arlavinda A. Lubis

Radiology Department,Ulin Hospital /Faculty of Medicine, Lambung Mangkurat University


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Introduction

The mediastinum is theregion in the chestbetween the pleuralcavities that containthe heart and otherthoracic viscera exceptthe lungs


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Mediastinal anatomy

Boundaries

Lateral - parietal pleura

Anterior - sternum Posterior - vertebral column and

paravertebral gutters

Superior - thoracic inlet

Inferior - diaphragm


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Felson ”Radiologists” Anterior mediastinal, is bounded anteriorly by

the sternum and posteriorly by a line drawn from the

anterior aspect of the trachea and along the posteriorheart border

Middle mediastinal compartment lies betweenthe anterior and posterior mediastinum

Posterior mediastinal, anterior border is

defined by a line that is 1 cm posterior tothe anterior edge of the vertebral bodies

Mediastinal compartmentby Felson


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(Meschan, 1981;

resited by Lange & Walsh, 2007)


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Diseases of the Mediastinum

Pneumomediastinum

Mediastinitis

Neoplasma


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Pneumomediastinum Air in the mediastinum is a common complication of

mechanical ventilation is also commonly encountered insome conditions

Pain is the most common symptom

Results from stretching of the mediastinal tissues

Substernal and aggravated by breathing and changing position

Dyspnea, dysphagia, subcutaneous crepitation


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Mediastinitis Acute inflammation of the mediastinum

Substernal chest pain, chills, high fever, prostration

Chronic mediastinitis


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Neoplasma


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Clinical Presentation

Asymptomatic mass

Incidental discovery – most common

50% of all mediastinal mass are asymptomatic 80% of such mass are benign

More than half are malignant if with symptoms


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Effects on Compression or invasion of adjacent tissues

Chest pain, from traction on mediastinal mass, tissue invasion,or bone erosion is common

Cough, because of extrinsic compression of the trachea orbronchi, or erosion into the airway it self

Hemoptysis, hoarseness or stridor

Pleural effusion, invasion or irritation of pleural space

Dysphagia, invasion or direct invasion of the esophagus

Pericarditis or pericardial tamponade

Right ventricular outflow obstruction and cor pulmonale


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Superior vena cava Vulnerable to extrinsic compression and obstruction because it is thin

walled and its intravascular pressure is low, and relatively confined bylymph nodes and other rigid structures

Superior vena cava syndrome Results from the increase venous pressure in the upper thorax , head

and neck characterized by dilation of the collateral veins in the upper portion of

the head and thorax and edema and phlethora of the face, neck andupper torso, suffusion and edema of the conjunctiva and cerebralsymptoms such as headache, disturbance of consciousness and visual

distortion Bronchogenic carcinoma and lymphoma are the most

common etiologies


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Hoarseness, invading or compressing the nerves

Horners syndrome, involvement of the sympathetic

ganglia [dropping eyelid, decreased pupilsize,decreased sweating on the ipsilateral face]

Dyspnea, from phrenic nerve involvement causingdiaphragmatic paralysis

Tachycardia, secondary to vagus nerve involvement

Clinical manifestations of spinal cord compression


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Systemic symptoms and syndromes

Fever, anorexia, weight loss and other non specific

symptoms of malignancy and granulomatousinflammation


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Computed tomography

Can identify normal anatomic variations and fluid filledcyst

Site of the origin of the mass can be better identified

100% specificity for the CT appearance of teratomas,thymolipoma, omental fat herniation

Overall accuracy for predicting mediastinal mass is only48%


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Computed tomography

Limitation

Horizontal oriented structures and boundaries are difficult to

evaluate

Abnormalities in the aortopulmonary window area and the

subcarinal area

CT has become the initial imaging procedure of choice for

evaluation of mediastinum in patients with primarymediastinal mass or with lung cancer


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Magnetic Resonance Imaging

Assesses tissue by measuring the radiofrequencyinduced nuclear resonance instead of measuring theattenuation of transmitted ionizing radiation

Coronal and sagittal planes are better viewed, verticalstructures and boundaries are better evaluated

Superior sulcus tumors, lesions invading themedistinum, chest wall and diaphragm

And possible invasion of the brachial plexus, andfor evaluating vertebral invasion


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Magnetic Resonance Imaging

Limitations

Distinguish poorly between hilar mass and adjacent

collapsed or consolidated lung

Cannot distinguish between a benign and a malignant causes

for lymph node enlargement


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Ultrasonography

For cystic nature of mediatinal mass

Useful in guiding endoscopic biopsy technique


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Radionuclide imaging

Rely on the localization of markers based on specificmetabolic or immunologic properties of the target tissue

Potential ability to diagnose and stage a malignancy andidentify distant metastasis

Planar imaging with gallium 67 and thallium-201


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POSITRON EMISSION TOMOGRAPHY

The single most notable addition to the staging armamentarium forthe evaluation of lung cancer

Based on the biologic activity of neoplastic cells

PET is a metabolic imaging technique based on the function of a tissue

rather than its anatomy Lung cancer cells demonstrate increased cellular uptake of glucose

and a higher rate of glycolysis when compared to normal cells

The radiolabeled glucose analogue [18F] fluoro-2-deoxy-d-glucoseundergoes the same cellular uptake as glucose, but after

phosphorylation is not further metabolized and becomes trapped incells

Accumulation of the isotope can then be identified using a PETcamera

Specific criteria for an abnormal PET scan are either a standard

uptake value of greater than 2.5 or uptake in the lesion that is greaterthan the background activity of the mediastinum

It has proved useful in dif ferentiating neoplastic from normal tissues


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POSITRON EMISSION TOMOGRAPHY

The technique is not infallible because certain non-neoplastic processes, including granulomatous andother inflammatory diseases as well as infections, may also demonstrate positive PET imaging

Size limitations are also an issue, with the lower limitof resolution of the study being approximately 7 to 8mm depending on the intensity of uptake of the

isotope in abnormal cells

One should not rely on a negative PET finding forlesions less than 1 cm on CT scan


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Dealing with mediastinal mass


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Conventional radiographic signs

The "silhouette sign“

The hilar overlay sign

The hilar convergence sign

The cervicothoracic sign


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Foto thoraks normal


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The "silhouette sign“

When a mass abuts a normal

mediastinal structure of similar

radiodensity, the margins of the 2

structures will be obliterated

This apparent loss of the margin

of the normal structure can be

used to localize a mediastinal

mass to the same compartmentas the normal structure


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The hilar overlay sign

especially useful indistinguishing an anteriormediastinal mass from a

prominent cardiac silhouette

If the bifurcation of the mainpulmonary artery is >1 cmmedial to the lateral border of

the cardiac silhouette, it isstrongly suggestive of amediastinal mass

Imaging of the mediastinum in oncology

Michele Lesslie, DO; Marvin H. Chasen, MD, MSEE; Reginald F. Munden, MD,

DMD


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The hilar convergence sign

is used to distinguish between a prominent hilum and anenlarged pulmonary artery

If the pulmonary arteries converge into the lateral borderof a hilar mass, the mass represents an enlargedpulmonary artery

A hilar mass may have the appearance of an enlargedpulmonary artery, but the vessels will not arise from themargin; instead they will seem to pass through themargins as they converge on the true artery


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an enlarged

pulmonary artery

Hillar mass


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The cervicothoracic sign

is used to determine the location of a mediastinal lesion in theupper chest

The uppermost border of the anterior mediastinum ends at thelevel of the clavicles.

the medial and posterior mediastinum extends above theclavicles. A mediastinal mass that projects superior to the levelof the clavicles must therefore be located either within the

middle or posterior mediastinum.

the more cephalad the mass extends, the more posterior thelocation


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The anterior mediastinum contains the following structures:thymus, lymph nodes, ascending aorta, pulmonary artery, phrenicnerves and thyroid.

The four T's make up the mnemonic for anterior mediastinalmasses::

1. Thymus

2. Teratoma (germ cell)

3. Thyroid

4. Terrible Lymphoma


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Sanjeev Bhalla, Marieke Hazewinkel and Robin Smithuis Cardiothoracic Imaging Section of the Mallinckrodt Institute of Radiology, St. Louis, USA and the Radiology

department the Medical Centre Alkmaar and the Rijnland Hospital, Leiderdorp, the Netherlands


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Lesions typically in the

Anterior Mediastinum

Thymic neoplasm Thymoma is the most common neoplasm occuring in the

anterior mediastinum Recognized more often recently because of increase

aggresiveness in evaluating patients with myasthenia gravis

Composed of lymphocytes and epithelial cells


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Thymoma

Peak incidence is 40-60 y/o

Equal gender predilection

Rare in children

2/3 assymptomatic at the time of diagnosis

Anterior mediastinal mass may be discovered incidentally

Chest pain, cough, dyspnea

40-70% of patients can have systemic syndromes


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Thymoma

Myasthenia gravis is the most common syndrome

Occurs in 10-50% of patients

How thymoma produced myasthenia is unknown butautoantibodies to the post synaptic acetylcholine receptorappears to explain the dysfunction of the neuromuscular junction


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Thymoma

Found near the junction of the heart and great vessels

Round or oval, smooth or lobulated as compared with

thymic hyperplasia which is symmetrical

Usually distorts the gland normal shaped


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Thymoma

Thymomas are neoplastic but most are benign

Invasive tumors have a poorer prognosis

5 year = 50-77% survival rate

10 year = 30-55% survival rate

Recurrence after resection occurs in 1/3 of patients

Presence of thymoma-associated systemic syndromeis a poor prognostic sign


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Thymoma

May respond to hormonal therapy

Manage by resection via median sternotomy approach or

VATS

Adjunctive treatment with post operative radiotherapy

Addition of perioperative radiotherapy is provided


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thymoma


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Other thymic mass

Thymic hyperplasia, thymic cyst and lipothymoma

Thymic carcinoma is a malignant process that invades

locally and frequently metastasized

Prognosis is poor

Resection followed by adjuvant chemoradiotherapy is

advocated


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Germ cell tumors

10-12 % of primary mediastinal tumors are derived fromgerminal tissues both in adults and in children

Teratoma and teratocarcinoma

Seminoma

Embryonal cell carcinoma

Choriocarcinoma

They are believed to arise from remnant multipotent germcells that have migrated abnormally during embryonicdevelopment


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Teratomas

Most common germ cell tumors

Made up of tissues foreign to the area in which they occur

Ectodermal derivatives predominate

When only the epidermis and its derivatives are present,the term dermoid cyst


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Teratomas

Young adults

But reported in all age groups

Men and women affected equally

80% are benign

1/3 are asymptomatic

Pain, cough, dyspnea

Hemoptysis if tumor erodes into a bronchus

Expectoration of differentiated tissue such as hair (trichoptysis) or sebaceousmaterials can occur

Can rupture in the pleural space and can cause ARDS or enter the

pericardium causing Pericardial Tamponade


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Teratomas

On CXR, Teratomas are smooth, rounded and wellcircumscribed if they are cystic and morelobulated and asymmetric if they are solid

Soft tissue, fat and calcification (occasionally fullyformed teeth and bone) can be seen on CT images

All teratomas should be resected as to the

uncertainty whether it is benign and possibility offurther enlargement and impingement onadjacent structures


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Germ cell tumor

Smooth, well-defined anterior mediastinal tumor with

heterogeneous attenuation associated with calcific

intratumoral nodules suggests a mediastinal teratodermoid


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Benign teratoma. A 30-year-old man developed mild chest

discomfort. ( Atlas of diagnostic oncology, Arthur T.

Skarin,2009)


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Seminomas

Seminoma (dysgerminoma)

Occurs almost exclusively in men

Usually in the 3rd decade of life

Chest pain, dyspnea, cough, hoarseness and dysphagia

SVC syndrome can occur

They are aggressive malignant tumors that extend locallyand metastasized distantly, usually to the skeletal bones


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Seminoma

They may secrete HCG, but not AFP

Poor prognosis Age >35 y/o

SVC syndrome Supraclavicular, clavicular or hilar adenopathy Presentation with fever

Extremely radiosensitive and may respond dramaticallywith chemotherapy even in cases of dissemination

Cisplatin based regimen is used Long term survival is 80%


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Lymphomas

Common cause in both adults and children

10-20% of cases

Hodgkin’s disease occurs bimodally in adolescents andyoung adults and in those over 50

Non-Hodgkin’s occurs in older adults

50-60% of HD have mediastinal lymph node involvementat the time of diagnosis

Only 20% of NHL have mediastinal involvement


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Lymphoma

Incidental discovery of a mass on CXR is a commonpresentation of lymphoma

Systemic and localized symptoms

Tracheal compromise and SVC are common

Pericardial and pleural involvement

Resection is not a necessary part of therapy, but anteriorthoracotomy or mediastinoscopy is required to confirmthe diagnosis if adenopathyis not evident outside themediatinum


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Obliterated retrosternal clear space

On the PA film there is a lobulated widening of

the superior mediastinum.On the lateral chest film the retrosternal clearspace is obliterated.

This happened to be a patient with lymphoma.


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Thyroid lesions

Ectopic thyrod gland accounts for 10% of mediastinal mass

Cervical goiter extends susternally into the anterior

mediastinum Primary intrathoracic goiter, originating from the

heterotropic thyroid tissue is rare

Most are in the anterior mediastinum but can occur in the

middle and posterior mediastinum


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Thyroid lesions

Common in women

Middle or older age

Asymptomatic

Hoarseness. Cough, swelling of the face

Recognized by radioactive iodine screning Resected by transcervical approach wihout the use of

sternotomy approach


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Parathyroid lesions

Mediastinal parathyroid tissue accounts for as many as10% of cases of hyperparathyroidism

Mediastinum is the most common site for ectopicparathyroid adenomas in surgically resistanthyperparathyroidism

Technetium scanning are accurate in diagnosingparathyroid tissue

Cured by complete resection


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Mesenchymal tumors

Iipomas, fibroma, mesothelioma, lymphangiomas,

They arise from connective tissue, fat, smooth

muscle, striated muscle, blood vessels or lymphaticchannels and can occur in a any region of themediastinum

Histologically they differ from their counterpart

Presence of symptoms means that the lesion ismalignant


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Lipoma

Is the most common mesenchymal tumor

Most often anterior

Encapsulted or unencapsulated

Smooth, rounded with sharply defined margins


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Lipomatosis

More common than lipoma

Generalized overabundance of histologically normal

unencapsulated fat The presence of some fat in the mediastinum is

normal, usually in and around the thymus

Accumulation of excess fat is associated withgeneralized obesity or Cushing”s syndrome or withthe use of exogenous steroids or drugs

Middle Mediastinum


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Middle Mediastinum

The middle mediastinum contains the following structures:lymph nodes, trachea, esophagus, azygos vein, vena cavae,posterior heart and the aortic arch.

The majority of middle mediastinal masses will consist offoregut duplication cysts (eg oesophageal duplication orbronchogenic cysts) or lymphadenopathy.Aortic arch anomalies can also present as middle mediastinalmasses.



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Middle Mediastinum

Enlargement of the lymph node

Mediatinal lymph node enlargement is most often due to

three categories of disease process Lymphomas

Metatastic cancer

Granulomatous inflammation


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On the left a patient with a small cell lung

carcinoma.

On the PA film there is a lobulated paratracheal

stripe on the right.

On the lateral radiograph there is a density overlying

the ascending aorta and filling the retrosternal

space.

These findings indicate a mass in the anterior aswell

as in the middle mediastinum.

CT scanning confirm of lymphoma.


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Developmental cyst

Comprise 10-20% of all mediatinal mass in both adults andchildren

Pericardial, bronchogenic and enteric cyst on the basis oftheir lining tissue

Bronchogenic and enteric cyst are referred to as foregutduplication cyst because of their origin from aberrant

portions of the ventral and dorsal foregut


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Developmental Cysts

Pericardial cyst

Accounts for 1/3 of cystic masses in adults

Less common in children

They typically lie against the pericardium, diaphragm oranterior chest wall on the right cardiophrenic angle

It can enlarge to cause right ventricular outflow tractobstruction, or rupture and hemorrhage to cause pericardialtamponade or sudden cardiac death


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Developmental Cysts

Bronchogenic cyst Found near the large airways, often posterior to the

carina, may attach to the esophagus or even inside the

pericardium Cyst wall often contains cartilages and respiratory

epithelum

Most are discovered incidentally and asymptomatic

They can communicate with the tracheobronchial tree

and can become infected and cause airway obstruction,pulmonary artery compression and hemodynamiccollapse or rupture with disastrous consequences


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Developmental Cysts

Enteric or entergenous cyst

Similar in location and appearance with bronchogenic cyst,

but have digestive tract epithelum

Uncommon in adults

Commonly seen in infants and children

Associated with spinal extension and malformation of the

vertebral column called neurenteric cyst


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Diaphragmatic hernia

The protrusion of omental fat or other abdominal contentsthrough the diaphragm may occur via several potentialroutes and medatinal mass lesion in any compartment

may occur

A hernia thorough the foramen of Morgagni produces acardiphrenic angle mass, usually on the right side


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Bochdalek’s hernia, in the posterior mediastinum,

generally appears on the left side, presumably because theliver prevents formation on the right

They are usually incidental finding but can causecomplication in some cases


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Posterior Mediastinum

The posterior mediastinum contains the following structures: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 innature.These can arise from the sympathetic ganglia (egneuroblastoma) or from the nerve roots (eg schwannoma orneurofibroma).


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Cervicothoracic sign


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On the left the MR of the same patient.

It turned out to be a schwannoma.


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Ganglioneuroma. During evaluation for unrelated problem, chest radiography in a 24-year-

old woman revealed an asymptomatic posterior mediastinal mass. Histologic showed

ganglioneuroma ( Atlas of diagnostic oncology, Arthur T. Skarin,2009)


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