mediastinal mass

JSS Medical College, Mysuru

CASE OF THE WEEK

DR KAVITHA K.DR SHIKHAR GARG

(Post Graduate Residents-Radiology)

PRESENTING COMPLAINT

27 year old man came with history of chronic dry cough. No h/o fever, hemoptysis, loss of weight.

He was referred to the radiology department for further evaluation.

What is the imaging modality?

What are your findings?

What is the imaging modality?

What are your findings?

What are your differential diagnosis?

FINDINGS

Chest X-Ray PA view shows a well defined round radio-opaque lesion in theleft perihilar region.

CHEST X-RAY - PA VIEW

SHARP BORDERS

OBTUSE ANGLE WITH LUNG

NO AIR BRONCHOGRAMS

Based on the findings of the radiograph we can say that it’s a medisatinal mass NO SILHOUETTING OF LEFT HEART BORDER

FINDINGS

DIFFERENTIAL DIAGNOSIS

The mass seems to be arising from left main bronchus.

LEFT LATERALX RAYLeft lateral xray of the chest showing a well defined radio-opaque lesion middle mediastinum abutting the left main bronchus and carina(arrowhead).

SO HOW DO WE DIFFERENTIATE MEDIASTINAL MASS FROM

PARENCHYMAL MASS?

MEDIASTINAL VS PARENCHYMAL MASS

• Unlike lung lesions, a mediastinal mass will not contain air bronchograms.

• Margins with the lung will be obtuse.

• Will not move with resipration on fluoroscopy.

• Pencil sharp borders.

• Broad based towards the mediastinum.

A lung mass abutts the mediastinal surface and creates acute angle with the lung.

• A mediastinal mass will sit under the surface of the mediastinum, creating obtuse angles with the lung.

SUPERIOR MEDIASTINUM

Above the level of the pericardium and plane of Ludwig.

INFERIORMEDIASTINUM

Below the plane of ludwig

Anterior mediastinum: Anterior to the pericardium

Middle mediastinum: Within the pericardium

Posterior mediastinum: Posterior to the pericardium 

DIVISIONS OF INFERIOR MEDIASTINUM

Anterior mediastinum Thymus, lymph nodes and retrosternal thyroid

CONTENTS OF INFERIOR MEDIASTINUM

Middle mediastinum The heart, Pericardium, Great vessels, Tracheal bifurcation and both main bronchi.Posterior mediastinum Descending aorta, Oesophagus, Thoracic duct, Azygous & hemiazygous venous systems.

LETS LEARN THE SIGNS WHICH HELP US TO LOCALISE A MEDIASTINAL MASS ON A FRONTAL RADIOGRAPH

 The differential attenuation of x-ray photons by two adjacent structures defines the silhouette

SILHOUETTE SIGN

Loss of right cardiac silhouette due tor right lung middle lobe pneumonia

When a mass arises from the hilum, the pulmonary vessels are in contact with the mass and their silhouette is obliterated.

Visible vessles implies that the mass is not contacting the hilum, and is either anterior or posterior to it.

HILUM OVERLAY SIGN

Helps to distinguish a bulky hilum due to pulmonary artery dilatation from a mass.

Vessels can be seen to converge and join a dilated pulmonary artery. 

HILUM CONVERGENCE SIGN

A CASE OF PULMONARY ARTERY HYPERTENSION

A mass in the posterior mediastinum, is surrounded by the lung tissue from all sides. This leads to a well-defined cephalic border seen above the clavicle

CERVICOTHORACIC SIGN

Negative cervico-thoracic sign- s/o posterior mediastinal mass

Well defined borders above the clavicle

ABDOMINO THORACIC SIGN

A thoracic lesion which has its caudal end visible below the dome of diaphragm must be in the posterior mediastinum.

Mass Extending below the Diaphragm

DIVISIONS ON LATERAL IMAGING

DIFFERENTIAL DIAGNOSES OF MEDIASTINAL MASSES

CT AND MRI WILL HELP US TO LOCALIZE, FURTHER CHARACTERISE VARIOUS MEDISTINAL MASS AND ALSO HELPS IN EVALUTING INVASION INTO ADJACENT STRUCTURES.

FURTHER IMAGING

Final conclusion: Well demarcated radio-opaque mass in the middle mediastinum arising from the left main bronchus.

BASED ON THE XRAY FINDINGS DIFFERENTIALS –

Oesophageal duplication cysts - Thick walled cysts found adjacent to the oesophagus

Bronchogenic Duplication cysts - Sharply demarcated round/ oval thin walled mass filled with proteinacious fluid usually in the medial 1/3 of lungs arising from the bronchus.

FINAL DIAGNOSIS

BRONCHOGENIC CYST

BRONCHOGENIC CYST

Bronchogenic cysts are congenital malformations of the bronchial tree.

They can present as a mediastinal mass that may enlarge and cause local compression.

It is also considered the commonest of foregut duplication cysts.

Bronchogenic cysts are asymptomatic and are found incidentally.

When large, mass effect may result in bronchial obstruction leading to air trapping and respiratory distress.  

CLINICAL PRESENTATION

Sharply demarcated round mass in the medial 1/3 of lungs.

They do not communicate with the bronchial tree, and are therefore not air filled.

They contain fluid ,variable amounts of proteinaceous material, blood products, and calcium oxalate . It is the latter three components that result in increased attenuation mimicking solid lesions.

FEATURES

CT findingsWell circumscribed spherical mass of variable attenuation  with variable fluid composition explaining the different CT attenuations observed.The degree of CT attenuation often depends on the amount of internal proteinaceous content .

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FURTHER IMAGING

MRI

T2WI High signal intensity due to fluid content